
COPl'RIGHT DEPOSm 



Ube laural /IDanuals 

Edited by L. H. BAILEY 



MANUAL OF TREE DISEASES 





Ube IRural /iDanuals 






Edited by L. H. BAILEY 






J' 




Manual 


OF Gardening — Bailey 




Manual 


OF Farm Animals — Harper 




Farm and Garden Rule-Book — Bailey 




Manual 


OF Fruit Insects — Slingerland and 


Crosby 


Manual 


OF Weeds — Georgia 




The Pbi] 


ning-Manual — Bailey 




Manual 


OF Fruit Diseases — Hesler and 


Whetzel 


Manual 


OF Milk Products — Stocking 




Manual 


OF Vegetable-Garden Insects — 


Crosby 


and 


Leonao'd 




Manual 


OF Tree Diseases — Rankin 




Manual 


OF Home-Making — Van Rensselae 


; Rose, 


and Canon 





MANUAL 



OF 



TREE DISEASES 



BY 



W. HOWARD RANKIN, A.B., Ph.D. 

ASSISTANT PROFESSOR OF PLANT PATHOLOGY 

NEW YORK STATE COLLEGE OF AGRICULTURE 

AT CORNELL UNIVERSITY 



THE MACMILLAN COMPANY 

1918 

All rights reserved 






Copyright, 1918, 
By the MACMILLAN COMPANY. 



Set up and electrotypcd. Published November, 1918. 



20 i9l8 



Nortooofi ^rrB2 

J. S. Gushing Co. — Berwick & Smith Co. 

Norwood, Mass., U.S.A. 



'CI.A5U8205 



PREFACE 

The steadily accumulating knowledge of the diseases of 
trees in the United States has never been brought together and 
made available to the general public. The intention of this 
Manual is to describe and suggest means of control for the 
tree diseases that have been most studied. Much remains to 
be learned about many of these diseases, and still many more 
have never been investigated. Therefore, in the treatment of 
this subject there are many unavoidable limitations which the 
trained reader will perceive. The diseases of fruit-trees, and of 
field and vegetable crops, have received the attention of plant 
pathologists in most parts of the country for many years. 
The results of these investigations have been made available 
to the growers of these crops in various ways. On the other 
hand, the diseases of forest, shade, and ornamental trees have 
been largely neglected until very recently. 

Tree diseases cause enormous losses in the large tracts of 
forests on which we depend for timber. The timber owner 
has been slow to adopt the fundamentals of scientific forest 
practice, and so far methods for the control of forest-tree 
diseases have not begun to operate in reducing losses. The 
owners of shade and ornamental trees are constantly con- 
fronted with diseases which they wish to control. They have 
become accustomed to controlling insects, but the funda- 
mentals involved in the appearance of a di;;ease and the meas- 
ures necessary to protect trees from further damage are largely 
puzzling to them. 

An understanding of the cause of disease is essential to the 
undertaking of adequate control measures. That the tree is 



VI PREFACE 

a living organism which requires water, food, air and sunHght 
is often overlooked. INIany of the diseases outside the forest 
are due to the failure to recognize the importance of main- 
taining suitable conditions for tree growth. The soil must 
contain the proper supply of food materials, and be of a texture 
which will conserve the water and air that are necessary for 
healthy root development. Pavements and sod are frequently 
never considered as the cause of the decline and death of trees. 
Likewise, it is seldom appreciated that the smoke and poisonous 
gases in the atmosphere in cities kill many trees. Also the 
appearance of leaf-spots, cankers, wood-rots and root-rots in 
no way explain themselves unless it is understood that in- 
visible parasitic plants are growing in the living tissues of the 
tree and causing their death. The technical facts regarding 
the relation between a tree and its environment are more easily 
comprehended than the life history of the parasites which cause 
diseases. Nevertheless, the tree owner must understand the 
nature of these organisms, the appearance of the symptoms 
they produce, and many other facts regarding diseases before 
he can intelligently attempt their control. It is hoped that 
the details concerning the diseases discussed in this book will 
assist to that end. The treatment has been made as simple 
as possible, and only the essentials regarding the disease, which 
are necessary to recognize and understand it, have been in- 
cluded. A glossary is appended, which will assist in explain- 
ing the more technical terms. 

It has been necessary to treat the general and specific diseases 
separately. Those diseases which are more or less common 
to all kinds of trees are discussed in the first four chapters. 
The more specific diseases will be found in the chapters follow- 
ing, which are arranged alphabetically according to the com- 
mon name of the various groups of trees. Cross-reference 
has been freely made in the different chapters to more complete 
discussions found elsewhere. This would be unnecessary if 



PREFACE Vll 

the book were to be read from cover to cover. The plan of the 
book is intended, however, to facilitate the diagnosis of a dis- 
ease of a certain kind of tree and to group the diseases of this 
tree in one place where comparisons may be made. Under 
each of the host-chapters, the diseases are arranged according 
to the part of the tree affected and will be found in the fol- 
lowing order : leaf, twig, branch, trunk and root diseases. 
The reader is advised to make free use of the index, which will 
facilitate the finding of those discussions unavoidably^ scattered. 

It is regretted that specific information is not yet available 
on many common tree diseases. Most of the leaf-spot diseases 
have not been studied. Likewise, control measures are largely 
limited to eradication methods, so far as definite recommenda- 
tions can be made. This apparently will always be the case 
for the diseases of the woody parts of trees, until means of 
naturally or artificially immunizing trees are devised. Spray- 
ing and dusting for leaf diseases w^ill be practicable when these 
diseases are better understood. Such methods are expensive, 
however, and their use will be limited for this reason. 

The author is indebted to Dr. F. D. Kern, who has read 
the discussions of the rust diseases and offered many helpful 
suggestions. Grateful acknowledgment is also made to Mrs. W. 
H. Rankin and to the following co-workers in the Department 
of Plant Pathology at Cornell University for many suggestions 
regarding the manuscript and for photographs loaned : Prof. H. 
H. Whetzel, Dr. L. R. Hesler, Dr. Donald Reddick, Dr. V. B. 
Stewart, Dr. C. T. Gregory, Dr. H. ]M. Fitzpatrick, and 
Miss Edwina Smiley. 

W. Howard Rankin. 

Cornell University, Ithaca, New York, 
September 1, 1918. 



CONTENTS 

CHAPTER I 

PAGE 

Seedling Diseases and Injuries 1 

Damping-off .......... 2 

Sun-scorch .......... 9 

Winter-drying . . . . . . . . . .11 

Freezing-to-death . . . . . . . . .12 

Smothering-disease 15 

CHAPTER II 

Leaf Diseases and Injuries 17 

Winter-drying .......... IS 

Late frost-injury . . . . . . . . .21 

Drought-injury and sun-scorch ....... 22 

Smoke- and gas-injury ........ 23 

Leaf-spots .......... 27 

Powdery mildews ......... 34 

Leaf-cast of conifers ......... 38 

Sooty molds .......... 41 

Silver-leaf .......... 41 

CHAPTER III 



Body and Branch Diseases and Injuries 
Freezing-to-death of twigs and bark 
Frost-cracks 
Sun-scald . 
Lichen-injury 
SHme-flux . 
Mistletoe diseases 
Electrical injuries 

ix 



45 
47 
50 
52 
52 
53 
54 
60 



CONTENTS 



Galls 
Wood-rots 



PAGE 

63 
64 



CHAPTER IV 

Root Diseases antd Injuries 
Drying and drowning 
Freezing-to-death 
Gas-injury . 
Shoe-string root-rot . 
Mycorhizas 
Roots parasitized by flowering plants 



72 

73 
74 
76 

78 
82 
84 



CHAPTER V 

Alder Diseases 86 

Powdery mildew of catkins ....... 86 

Catkin-deformation ......... 87 

Brown checked wood-rot ........ 87 

Common white wood-rot ........ 87 

Root-tubercles 88 



CHAPTER VI 



Arbor-vit.e Diseases 
Seedling-blight . 
Leaf-blight 

Brown pocket heartwood-rot 
Red-brown root- and butt-rot 



89 
89 
90 
91 
91 



CHAPTER VII 

Ash Diseases 93 

Leaf- and twig-rust ......... 93 

White heartwood-rot 95 

CHAPTER VIII 

Bald Cypress Diseases 97 

Pecky heartwood-rot 97 



CONTENTS 



XI 



CHAPTER IX 



Basswood Diseases 
Powdery mildew 
Leaf-spot . 
White sapwood-rot 
Southern root-rot 



PAGE 

101 
101 
102 
103 
103 



CHAPTER X 



Beech Diseases 

Yellowish sapwood-rot 
Common white wood-rot 
Uniform white sapwood-rot 
White butt-rot . 
Parasitized roots 



105 
105 
107 
108 
108 
108 



CHAPTER XI 

Birch Diseases Ill 

Leaf rust Ill 

Yellow leaf -blister 112 

Red leaf-blister 112 

Powdery sapwood-rot . . . . . . . .113 

Yellowish sapwood-rot 115 

Common white wood-rot . . . . . . . .115 

Brown heartwood-rot . . . . . . . .116 

White butt-rot 117 



CHAPTER XII 




Buckeye Diseases 


. 118 


Leaf-blotch 

Powdery mildew ........ 

Cm-led leaf -blight and witches '-broom .... 

White sapwood-rot ........ 


. 118 
. 121 
. 121 
. 122 


CHAPTER XIII 




Butternut Diseases 


. 123 


Leaf-spot 


. 123 



xii CONTENTS 

PAGE 

Common white wood-rot 124 

Brown checked wood-rot 124 

CHAPTER XIV 

Catalpa Diseases 125 

Yellowish wood-rot . • 125 

Brown butt-rot 127 

CHAPTER XV 

Cedar Diseases . . • 129 

Eastern leaf-rust ......... 129 

Western leaf-rust 130 

Brown felt-blight 130 

Eastern witches'-broom 131 

Western twig-blight and witches'-broom 133 

Branch-swellings 134 

Pecky heartwood-rot 135 

CHAPTER XVI 

Chestnut Diseases 138 

Large leaf-spot . . . . . . . • • .139 

Twig-blight 140 

Endothia canker 140 

Strurtiella canker . 148 

Brown checked wood-rot ........ 149 

Straw-colored heartwood-rot . 149 

White piped butt-rot 150 

CHAPTER XVII 

Elm Diseases 152 

Leaf-spot • 152 

Powdery mildews 153 

Brown wood-rot 154 

CHAPTER XVIII 

Fir Diseases 155 

Leaf blister-rusts 155 



CONTENTS xiii 

PAGE 

Leaf-rusts 159 

Leaf-cast 159 

Rust witches'-broom ......... 160 

Gray mold twig-blight ........ 161 

Mistletoe burl and witches'-broom 163 

Pecky wood-rot . . . . . . . . . .163 

Red-brown sapwood-rot . . . , . . . .165 

Stringy red-brown heartwood-rot 166 

Brown pocket heartwood-rot ....... 168 

Brown heartwood-rot ........ 169 

Brown root- and butt-rot 169 

Red-brown root- and butt-rot 170 

Yellow root-rot 170 



CHAPTER XIX 

Hackberry Diseases 173 

Powdery mildews . . . . . . . . .173 

Witches'-broom 174 

CHAPTER XX 

Hemlock Diseases 177 

Seedling root-rot 177 

Leaf-blight 179 

Brown-mold leaf-blight ........ 180 

Leaf and cone blister-rusts ....... 180 

Leaf-, cone- and twig-rusts 182 

Red-brown sapwood-rot ........ 184 

Stringy red-brown heartwood-rot ...... 184 

Brown pocket heartwood-rot ....... 184 

Cuboidal wood-rot ......... 185 

Red-brown root- and butt-rot 187 

CHAPTER XXI 

Hickory Diseases 188 

Leaf-mildew and witches'-broom ...... 188 

Common white wood-rot ........ 189 



XIV CONTENTS 

CHAPTER XXII 

PAGE 

Juniper Diseases 190 

Seedling twig-blight 190 

Leaf- and stem-rusts (general) 192 

Leaf- and twig-rusts 196 

Cedar-apples 197 

Rust witches'-brooms . . 200 

Branch-galls 200 

Fusiform branch-swellings 202 

White bark 204 

Brown pocket heart wood-rot ....... 204 

White pocket heartwood-rot ....... 206 

Yellow wood-rot . . . . . . . . . 208 

Stringy brown wood-rot ........ 209 

Basal heartwood-rot 210 

CHAPTER XXIII 

Larch Diseases 212 

Seedling root-rot ......... 212 

Leaf-rusts 212 

Mistletoe burl and witches'-broom ...... 214 

Pecky wood-rot 215 

Red-brown sap wood-rot . . . . . . . .215 

Brown heartwood-rot ........ 216 

Brown pocket heartwood-rot ....... 217 

Red-brown root- and butt-rot . . • . . . .217 

Yellow root-rot 218 

CHAPTER XXIV 

Locust Diseases 219 

Yellow wood-rot 219 

Brown checked wood-rot . . . . . . . .221 

Root-tubercles .......... 222 

CHAPTER XXV 

Maple Diseases 223 

Tar leaf-spot 223 



CONTENTS 



XV 



Black-specked leaf-spot 

Leaf-spots . 

Powdery mildews 

Leaf-blight 

Canker 

Wilt . 

Common white wood-rot 

Browni checked wood-rot 

White strand wood-rot 

Uniform white sapwood-rot 

White streaked sapwood-rot 

White butt-rot . 



PAGE 

225 
226 
227 
228 
229 
231 
232 
232 
233 
234 
235 
236 



CHAPTER XXVI 

Oak Diseases 237 

Leaf-blight 237 

Leaf-blister 239 

Powdery mildews . . . . . . . . .241 

Brown mildew .......... 243 

Large leaf-spot 243 

Twig-blight 244 

Strumella canker 245 

Brown checked wood-rot ........ 247 

Common white wood-rot ........ 250 

White pocket heartwood-rot 250 

String and ray butt-rot 252 

Wet heartwood-rot ......... 254 

Honeycomb heartwood-rot 255 

Soft heartwood-rot 257 

White piped butt-rot 258 

Straw-colored butt-rot 259 

White wood-rot 260 

White butt-rot 260 

White root-rot . ^ 261 

CHAPTER XXVn 

Pine Diseases 264 

Seedling root-rot 264 



XVI 



CONTENTS 



Leaf blister-rusts 265 

Leaf-rust 270 

Leaf-cast of white pine 270 

Brown felt-blight 271 

Leaf-cast and witches'-broom of western yellow pine . . 271 

Twig-blight 272 

Mistletoe burls and witches'-brooms 273 

Blister-rust of five-needle pines ....... 274 

Sweet-fern rust 281 

Comandra^-ust .......... 283 

Castilleja'-rust 285 

Oak rust 287 

Piiaon blister-rust 290 

Basal canker 290 

Pecky wood-rot • . . . .291 

Red-brown sapwood-rot ........ 292 

Brown heartwood-rot 292 

Brown pocket heartwood-rot ....... 293 

Red-ray wood-rol 293 

Red-brown root- and butt-rot 294 

Yellow root-rot .......... 296 

Brown root- and butt-rot 296 

CHAPTER XXVIII 



Poplar Diseases 
Leaf-rusts . 
Powdery mildew 
Yellow leaf-blister 
Catkin-deformation 
Canker 
Limb-gall . 

Common white wood-rot 
White pocket heartwood-rot 
White butt-rot . 



298 
298 
300 
300 
301 
301 
304 
304 
310 
310 



CHAPTER XXIX 



Spruce Diseases 

Seedling twig-blight 



313 
313 



CONTENTS 








xvu 


PAGE 


Leaf blister-rusts .315 


Leaf-rust . 












. 316 


Brown felt-blight 












. 317 


Leaf- and twig-blight 












. 319 


Cone-rust . 












. 320 


Rust witches'-brooms 












. 320 


Mistletoe witches'-broom 












. 321 


Pecky wood-rot 












. 324 


Red-brown sapwood-rot 












. 327 


Stringy red-brown heartwood-rot 










. 328 


Brown pocket heartwood-rot 










. 328 


Cuboidal wood-rot 










. 329 


Brown root- and butt-rot . 










. 329 


Red-brown root- and butt-rot . 










. 331 


Yellow root-rot . 












. 331 



CHAPTER XXX 

Sycamore or Plane Tree Diseases 333 

Leaf- and twig-blight 333 

CHAPTER XXXI 

Walnut Diseases 339 

Leaf-spot ........... 339 

Common white wood-rot ........ 339 

Brown checked wood-rot 340 





CHAPTER XXXH 




Willow Diseases . 




. 341 


Powdery mildews 




. 341 


Leaf-rusts . 




. 341 


Tar leaf-spot 




. ■ .343 


Common white w 


ood-rot ...... 


. 343 


White wood-rot 


CHAPTER XXXni 


. 344 


Tree Surgery 


• • 


. 345 


Pruning 




. 346 



XVlll CONTENTS 

PAGE 

Disinfecting wounds 348 

Wound dressings ......... 348 

Lesion excision .......... 351 

Cavity treatments 353 

CHAPTER XXXIV 

Spraying and Dusting for Leaf Diseases .... 357 

Appendix 361 

Common names of trees ........ 361 

Synonymy of polypore names ....... 364 

Glossary 365 

General bibliography of tree diseases ...... 367 

Index 371 



ILLUSTRATIONS 



1. Frost-crack in a maple ...... 

2. Frost-crack healed over in summer .... 

3. Mistletoe growing on white fir . 

4. Galls on branch of oak ...... 

5. Polypore fruiting-body showing spores 

6. Shoe-string root-rot on pine ..... 

7. Young toadstools of Armillaria mellea 

8. Mature fruiting-body of shoe-string root-rot fungus . 

9. Ash rust 

10. Leaf-spot of basswood (by V. B. Stewart) 

1 1 . Fruiting-body of Forties fomentarius .... 

12. Beech wood decayed by Fomes applanatus 

13. Fruiting-body of Polyporus betulinus 

14. Leaf-blotch of horse chestnut 

15. Leaf-spot of butternut ...... 

16. Brown felt-blight 

17. Endothia canker of chestnut ..... 
IS. Mycelial fans between bark and wood 

19. Spore-horns of chestnut canker fungus 

20. Perithecial stage of chestnut canker fungus 

21. Leaf-spot of elm (by H. M. Fitzpatrick) . 

22. Powdery mildew of elm ...... 

23. Pecky wood-rot, early stage ..... 

24. Pecky wood-rot in Douglas fir . 

25. Fruiting-body of Echinodontium tincforbun 

26. Brown heartwood-rot of Douglas fir . 

27. Fruiting-bodies of Rhizina iindulata (after Fitzpatrick) 

28. Cuboidal wood-rot of hemlock (by G. F. Atkinson) . 

29. Cedar-apple fungus on wild apple leaves (after Weimer) 

30. Cedar-apple fungus on haw leaf .... 

31. Cedar-apples — early stages of development (after Weimer) 

32. Cedar-apples in late autumn (after Weimer) 

33. Cedar-apple in spring with spore-horns (after Weimer) 



XX 



ILLUSTRATIONS 



(by H. M. 



34. Fruiting-bodies of Forties roseus 

35. Friiiting-body of Foines rimosus 

36. Tar leaf-spot of maple ..... 

37. Leaf-spot of maple caused by Phyllosticta minima 

38. Leaf-spot of maple caused by Glo'osporium apocryptum 

Fitzpatrick) ...... 

39. Leaf-blight of maple ...... 

40. Nectria canker on maple 

4L Sections through Nectria canker on maple 

42. Sections through trunk of maple affected by wilt 

43. Section tlirough fruiting-body of Ilydnum septentrionale 

44. Leaf-blight of oak 

45. Leaf-bhster of oak (by H. H. Whetzel) 

46. Powdery mildew on oak leaf (by G. F. Atkinson) 

47. Twig-canker on oak ...... 

48. Brown checked wood-rot in oak (by G. F. Atkinson) 

49. Fruiting-bodies of Polyporus sulphureus 

50. Fruiting-body of Polyporus Berkeleyi 
5L Fruiting-body of Polyporus dryadeus 

52. Blister-rust on twig of white pine (after Hesler and Whetzel) 

53. Blister-rust on trunk of white pine 

54. Uredinial stage of Cronartium ribicola on currant (after . 

Whetzel) 

55. Telial stage of Cronartium ribicola on currant (after 

Whetzel) 

56. Blister-rust on lodgepole pine .... 

57. Limb-galls on poplar ..... 

58. Common white wood-rot (after Hesler and Whetzel) 

59. Fruiting-body of Fomes igniarius 

60. Fruiting-body of Fomes igniarius (form called Fomes 
6L Section through fruiting-body of Fames igniarius 

62. Witches'-broom on black spruce 

63. Mistletoe witches'-brooms on black spruce 

64. Pecky wood-rot in spruce 

65. Pecky wood-rot, advanced stage 

66. Leaf-blight of sycamore ..... 

67. Sycamore tree defoliated by leaf-blight fungus (by M. 

68. Cankers on small sycamore twigs 

69. Cankers on limbs of sycamore .... 

70. Powdery mildew on willow leaves (by G. F. Atkinson) 



Hesler and 



Hesler and 



nigricans) 



F. Barrus) 



MANUAL OF TREE DISEASES 



MANUAL OF TREE DISEASES 

CHAPTER I 

SEEDLING DISEASES AND INJURIES 

From the very beginning of the hfe of a tree, the seedHng is 
subject to many more or less serious diseases. Damping-off 
may cause death, even before the tiny plant has grown above 
the surface of the soil. Later, if damping-off is avoided, va- 
rious blights are common in the seed- and transplant-bed. 
Although many pathogenes are known to cause seedling dis- 
eases, it is very difficult for the layman to identify the trouble 
any more accurately than by the general symptoms of damping- 
off or blight. Damping-off symptoms are mostly due to the 
activities of specific soil-harbored fungi. Blight symptoms 
may be produced by various rapidly spreading fungi, or by 
adverse moisture and temperature conditions. After a careful 
comparison of the blight symptoms produced by environmental 
conditions, with the usual symptoms caused by parasites, 
the layman should be able to distinguish between these two 
general types of seedling blights. In some cases, the seedlings 
of certain kinds of trees are affected by well-known specific 
leaf-, stem- or root-parasites which cause blight. These dis- 
eases are described in the chapter on the diseases of the species 
of tree affected. Otherwise, the damping-off and blights such 
as sun-scorch, winter-drying and freezing-to-death of seedlings 
of both coniferous and deciduous trees, are treated below. 

B 1 



2 MANUAL OF TREE DISEASES 

Damping-Off 
Caused by various species of fungi 

The damping-off diseases have commanded serious atten- 
tion from all persons who have attempted to grow seedlings, 
especially of conifers. Schreger, in an early compilation of the 
facts known about tree diseases, published in 1795, writes about 
the damping-off of beech seedlings. Since the growing of large 
quantities of seedlings for forest planting was first attempted in 
Europe, the earlier literature on damping-off appeared mostly in 
foreign languages. American nurserymen have grown small 
quantities for ornamental and shade tree stock for many years. 
The increasing demands for large quantities for forest planting 
were not supplied, however, by the production of the commer- 
cial nurserymen. It is thought that the small quantity pro- 
duced and high prices demanded for the stock were due mainly 
to the difficulties of handling the damping-off diseases. To-day 
the growing of coniferous seedlings in federal and state nurseries 
has developed until millions of trees are produced yearly. It 
was during the development of these specialized nurseries that 
the damping-off diseases in this country were studied, and 
methods evolved for their control. 

Damping-off is a universal seedling trouble. The fungi 
causing the disease are common soil-harbored organisms asso- 
ciated with decaying plant material. Seedlings grown in new 
soil may suflFer from damping-off as severely as those in beds 
which produced diseased plants the previous year. The seed- 
lings of coniferous trees in general show marked susceptibility, 
while those of deciduous trees are less often attacked. Beech 
and maple seedlings, however, often suffer. When no pre- 
cautions are taken, damping-off may kill practically the entire 
stand of seedlings, especially when large numbers are grown 
under crowded conditions. 



SEEDLING DISEASES AND INJURIES 3 

Symptoms. 

The critical period in the development of tree seedlings, so 
far as damping-off is concerned, extends from the time of the 
germination of the seed until the stem-tissues become woody, 
— a period of one or two months. Usually the first indication 
of damping-off is a water-soaked or brown area of decaying 
tissue in the stem, near the surface of the ground. If the dis- 
ease occurs very early in the development of the plants, the 
stems may be killed before their tips emerge from the ground. 
Often, also, the lesion originates just below the surface of the 
soil after the plant has pushed out, and wilting of the plant is 
the first sign of the trouble. Wherever the lesion may occur, 
the diseased stem-tissue soon collapses and allows the plant to 
fall over," while further disintegration of the tissue results in 
the death of the seedling. Root-rot may accompany damping- 
off and often is only another indication of the work of the same 
fungus. In the case of deciduous trees, especially the beech, 
the first lesions may show as cotyledon-spots. These lesions 
soon enlarge, however, so that the stem is involved and damping- 
off' follows. Under conditions favorable for the development 
of damping-off fungi, large circular areas of dead plants appear 
and only a few days are sufficient for the spread of the patho- 
gene from a few centers to all parts of the seed-bed. 

Cause of damping-off. 

Numerous species of fungi have been found to cause damp- 
ing-off. In general these fungi have no restricted host-range, 
and are so prevalent and omnivorous that seedling crops uni- 
versally suffer. In this country most of the vfork on these 
diseases has been done with conifers. Numerous species and 
forms of fungi belonging to the genus Fusarium have been 
found to be the most common cause. Pythium debaryanum 
Hesse and species of Rhizoctonia have also been found to be 
important damping-off pathogenes in certain cases. In Europe, 



4 MANUAL OF TREE DISEASES 

Phytojjhthora omnivora de Bary is the most common on both 
coniferous and deciduous tree seedHngs. This latter fungus is 
widely distributed in this country and may be found to be of 
importance with further investigations on deciduous seedlings. 
It is to be assumed that many other species of fungi may also 
at times produce damping-of¥ in tree seedlings, since Thielaoia 
basicola (B. and Br.) Zopf and species of Botrytis, Colle- 
totrichum, Volutella and other fungi have been discovered 
producing this disease in seedlings of other crops. Numerous 
inoculation experiments by various workers have established 
the power of the above mentioned pathogenes to cause this 
type of disease. 

The causal fungi represent many widely different types of 
life history. The parasitism of these fungi is of a very primi- 
tive sort. This is evidenced by their usual saprophytic char- 
acter, extreme destructiveness to the host-plant, wide host- 
range and the fact that they are limited in their activities to 
very young seedlings, which have not developed the more com- 
plex physical and chemical nature of older plants. These 
fungi exist ordinarily as common saprophytes on decaying 
vegetable matter in the soil and thus their mycelium is the 
main infective material. Various types of spores are formed 
by the different species of fungi concerned in damping-off, but 
they are rarely instrumental in the inoculation of healthy 
plants. These spores, however, are mainly useful in carrying 
the fungus over winter and through other conditions detrimental 
to vegetative growth. The entire life history of these fungi 
then, so far as explaining the appearance and development of 
damping-off in seedling-beds, is confined largely to the growth 
of the mycelium through or on the surface of the soil, from one 
plant to another. This manner of spreading is often well il- 
lustrated when all the plants in a single row are destroyed and 
only occasional plants in the adjacent rows are affected. Al- 
though some one or several of the damping-off fungi are generally 



SEEDLING DISEASES AND INJURIES 5 

present in all soils, their presence may not become evident if 
conditions are adverse to their development. All damping-off 
pathogenes are markedly influenced by temperature, soil 
moisture and the humidity of the atmosphere. A relatively 
high temperature, moist and compact soil and a humid at- 
mosphere furnish ideal conditions for these fungi, while lower 
temperatures and drier conditions of soil and atmosphere may 
check successfully a destructive development of these organisms 
after some damage has already been accomplished. 

Control. 

Since damping-off may be caused by any one of numerous 
species of fungi and may occur imder such variable conditions, 
no general rules for treatment can be prescribed which will 
apply in all cases. The control of damping-off may be effected 
by one of two general methods : (1) protection of the seedlings 
by maintaining conditions of temperature and moisture which 
interfere with the destructive development of the pathogenes ; 
(2) eradication of the pathogenes from the soil of the seed-bed 
by means of disinfectants. 

(1) Protection. 

Every investigator agrees that much can be accomplished 
in the control of damping-off by giving careful attention to 
the manipulation of soil moisture, temperature and atmospheric 
humidity. At the same time, it is realized that one may 
find it difficult, in regulating the amount of moisture and 
other factors, to preserve the equilibrium necessary to grow 
seedlings, and at the same time to prevent the growth of the 
fungi. The following method of procedure is advised : 

Each seed-bed should be provided with upright frame, with 
wire-mesh sides and removable top, which can be made into 
half-shade or full-shade by laying on laths. 

The seed should be sown on the surface of the prepared 
soil and covered to the desired depth with clean dry sand 



6 MANUAL OF TREE DISEASES 

obtained by digging three or four feet below the surface. This 
furnishes a surfacing for the bed which is sterile and easy to 
keep relatively dry. 

The beds should be covered and kept moist enough to pro- 
mote germination. After the seeds have germinated, partial 
shade should be furnished on bright days but should be removed 
in cloudy weather, in order to allow as much evaporation as 
possible from the surface of the soil. These precautions are 
especially important if it is warm and rainy. If the surface 
of the soil does not dry sufl&ciently, more clean coarse sand may 
be scattered over it. 

(2) Eradication. 

Two general eradication methods are recommended for the 
control of damping-off : (1) disinfection of the soil before 
planting, usually with formaldehyde; and, (2) for coniferous 
seedlings only, disinfection at the time of planting with sulfuric 
acid. 

If damping-ofF has previously occurred in a bed, the best 
practice is to remove the top-soil and substitute new soil. This 
is desirable since a large accumulation of the resting spores of 
the causal pathogene is to be expected after a severe outbreak. 
The following steps are essential for thorough disinfection : 

A solution of formalin should be made by adding one gallon 
of formalin (which should contain forty per cent formaldehyde 
by volume) to fifty gallons of water. 

The soil should be prepared by forking or raking. The 
formalin solution may then be applied to the bed with a sprin- 
kling-can, using about two quarts for every square foot of soil 
to be treated. If the nature of the soil is such that this amount 
cannot be put on in one application, as much as possible should 
be applied without making the soil muddy and the remainder 
added a few hours later. 

The bed should be covered as securely as possible with 
heavy paper or other impervious material for forty-eight hours. 



SEEDLING DISEASES AND INJURIES 7 

The active substance in the formaUn sokition is liberated as a 
gas (formaldehyde). The cover is necessary in order to retain 
this gas in the soil for a period sufficient to kill the pathogenes. 

Three or four days after the cover is removed, the soil should 
be thoroughly forked and allowed to stand in a loosened con- 
dition for another day or two, after which the bed may be 
prepared for sowing the seed. It is important to time the 
application of the formalin so that the seed may be sown as 
soon as the operations above described are completed, since 
the soil may become contaminated again from surrounding 
soil. Experience shows that beds contaminated after dis- 
infection may exhibit greater loss than those not disinfected. 
The increased virulence of damping-off fungi in disinfected 
beds is thought to be due to the lack of competition with 
other soil organisms which have been killed by the disin- 
fectant. With ordinary care, however, under most condi- 
tions a clean crop of seedlings is assured if the disinfection 
is thorough. Even after carefully disinfecting the soil, all 
the measures advised above under Protection should be ob- 
served (see page 5). 

The application of sulfuric acid to the soil at the time of 
seeding has given good results in controlling damping-off in 
coniferous seed-beds. Sulfuric acid should never be used on 
deciduous seedlings. The amoimt of acid used with safety 
will necessarily vary with the natural acidity or alkalinity of 
the soil. A too heavy application of sulfuric acid will cause 
injury to the seedlings. This method is more difficult to handle 
than the formalin treatment because in loose sandy soils the 
capillary movement of the water will bring the acid to the 
surface and produce there a concentrated solution, which must 
be counteracted by daily watering. With heavier soils, no wa- 
tering seems necessary from the experiments so far reported. 
With the two uncertain factors in mind, the natural acidity 
or alkalinity and the physical nature of the soil to be treated, 



8 MANUAL OF TREE DISEASES 

the grower must experiment under his own conditions before 
applying this method generally, else the chemical injury by 
the acid to the seedlings may be greater than the losses due to 
damping-off if no treatment were used. If this method can 
be .handled without damaging the seedlings, two special ad- 
vantages are gained over the other two methods given above. 
In the first place, dicotyledonous weeds rarely grow in the acid 
soil and the saving of the expense of weeding will often pay for 
the treatment. Secondly, the disinfectant is present in the soil 
throughout the critical damping-off period. This assures 
complete control since contamination of the beds from neigh- 
boring soil is not possible and, moreover, conditions of tempera- 
ture and moisture favorable to seedling growth can be provided 
without danger. 

The average amount of sulfuric acid is three-sixteenths of a 
fluid ounce of clear commercial sulfuric acid to each square 
foot of soil to be treated. A solution is made by adding three - 
sixteenths of an ounce of the sulfuric acid to each quart of water 
(this is at the rate of one part of acid to 170 parts of water). 
This solution should then be applied when the seed is sown 
at the rate of one quart to each square foot of soil. If the soil 
is light and sandy and conditions are favorable for excessive 
evaporation, light watering once or twice a day may be neces- 
sary to prevent acid-injury. In heavier soils no watering 
may be necessary. The strength recommended above is suffi- 
cient to disinfect a soil which is not strongly alkaline. If the 
soil is naturally acid, the three-sixteenths of an ounce to each 
square foot may be too much. It would, therefore, be advisable 
to divide a given bed into three parts, applying sulfuric acid to 
each part respectively in the following quantities, one-eighth, 
one-fourth and three-sixteenths of an ounce in a quart of water 
to each square foot. From this experiment it may be deter- 
mined which strength can be safely employed under the exist- 
ing soil conditions. 



SEEDLING DISEASES AND INJURIES 9 

References on Damping-Ofp 

Hartley, Carl, and Pierce, R. G. The control of damping-off of conif- 
erous seedlings. U. S. Dept. Agr. Bui. 453 : 1-32, pis. 1-2, fig. 1 
1917. 

Johnson, James. The control of damping-off disease in plant beds. 
Wisconsin Agr. Exp. Sta. Research Bui. 31 : 29-61, figs. 1-12. 
1914. 

Gifford, C. M. The damping off of coniferous seedlings. Vermont 
Agr. Exp. Sta. Bui. 157 : 143-171, pis. 1-4, figs. 1-10. 1911. 

Jones, L. R. The damping off of coniferous seedUngs. Vermont Agr. 
Exp. Sta. Ann. Rept. 20 : 342-347. 1908. 

Hartley, Carl. Injury by disinfectants to seeds and roots in sandy 
soils. U. S. Dept. Agr. Bui. 169: 1-35, pi. 1, figs. 1-2. 1915. 

Spaulding, Perley. The damping-off of coniferous seedlings. Phyto- 
pathology 4 : 73-88, pi. 6, figs. 1-2. 1914. 

Hartley, Carl, and Merrill, F. C. Preliminary tests of disinfectants 
in controlling damping-off in various nursery soils. Phyto- 
pathology 4 : 89-92. 1914. 

Pettis, C. R. Problems in nursery practice. Proc. Soc. Amer. Fores- 
ters 4 : 43-44. 1909. 

Scott, Chas. A. A practical method of preventing the damping-off 
of coniferous seedlings. Jour. Forestry 15 : 192-196, pis. 1-2. 
1917. 

Sun-Scorch 

Caused by over-transpiration and dry soils 

Under the crowded conditions which usually exist in the 
• seed- and transplant-beds, damage from sun-scorch is common 
and often destructive. Next to damping-off, sun-scorch is 
probably the most important general nursery trouble. A care- 
ful analysis of the causal conditions and the resulting behavior 
of the affected plants should make a case of sun-scorch relatively 
easy of diagnosis. For a discussion of this type of injury in 
older trees, see page 22. 

Symptoms. 

The entire plants or only the tops may be killed. The area 
of the beds involved where the entire plants are killed may be 
more or less circular. Contrary to the action of parasites, how- 



10 MANUAL OF T'REE DISEASES 

ever, the trees over the affected area die simultaneously and 
there is no progressive enlargement of the area. When only 
the tops of the plants or the lower and older leaves die, the 
plants may recover, though they remain in a weakened con- 
dition and easily succumb to later sun-scorch conditions. 
The affected leaves become chlorotic, turn yellowish and then 
become dried and dark brown. The entire needles are not 
always involved and it is very common to find only the tips 
brown and dead. An accompanying symptom of sun-scorch 
is found in the roots, which die previous to the appearance of 
the symptoms in the tops. At the time the leaves are turn- 
ing yellow, the root system already shows considerable injury. 

Cause. 

Sun-scorch results when the amount of water in the soil is 
not sufficient to replace rapidly the amount of water lost by 
excessive transpiration from the leaves. The extreme combina- 
tion of conditions bringing about sun-scorch are sandy soil 
and continuous hot, dry winds, with little dew at night, and 
little rainfall. Under these environmental conditions the 
crowding of large numbers of trees into a small space and the 
lack of any shade during a part or the whole of the day predis- 
pose the plants to sun-scorch injury. Certain species of trees, 
such as Norway spruce and Douglas fir, are more susceptible 
than others, especially if they are growing in soil which is 
rapidly drained, as is the case in the center of arched beds. 
The injury develops rapidly and conclusive evidence as to the 
causal conditions should be obtainable by examining the amount 
of water present in the soil. The soil around the roots of the 
affected plants will usually be found much drier than that 
around adjacent healthy plants. There may be a sufficient 
total water supply above and below the rooting region, but 
if this supply is not readily available, the plants will suffer 
when transpiration is excessive. 



SEEDLING DISEASES AND INJURIES 11 

Control. 

The most direct and effective measure to insure prevention 
or control of sun-scorch is heavy watering. The index as to 
frequency and amount of water to supply may be obtained 
by examining daily the actual water-content of the layer of 
soil in which the roots are growing. Light watering at fre- 
quent intervals may make the beds appear well watered, while 
actually the water may be lost in evaporation and never reach 
the roots of the plants in any quantity. 

A great saving in watering and a partial protection from 
sun-scorch may be easily obtained by erecting lath half-shade 
screens over the beds. Shading has often been used success- 
fully to halt further sun-scorch after it has once appeared. 

References 

Hartley, Carl. The blights of coniferous nursery stock. U. S. Dept. 

Agr. Bui. 44 : 1-21. 1913. 
Stone, G. E. Sun scorch of the pine. Massachusetts Agr. Exp. Sta. 

Ann. Rept. 22 : 2 : 65-69. 1910. 

WiNTER-D R YING 

Caused by the simultaneous occurrence of low soil temperatures and 
high air temperatures 

Conifers are subject to the death of the whole or part of the 
tree, during the winter months. The symptoms of winter- 
drying are similar to those of sun-scorch, discussed on page 9. 
The cause is also similar in that a sufficient intake of water to 
compensate for that lost in transpiration is impossible, because 
of the frozen condition of the soil. In sun-scorch, sufficient 
water is not present in the soil and in winter-drying, although 
the soil is saturated, the water is not available in the form of 
ice. Consequently when the air is warm, larger quantities of 
water are lost by the leaves than can be replaced. For a further 
discussion of this injury to older trees, see page 18. 



12 MANUAL OF TREE DISEASES 

Protecting the plants by mulching is an efficient means of 
preventing winter-drying. Where sufficient snow falls early 
in the winter, the beds may then be covered with burlap and 
the snow-mulch retained. Where more open winters are en- 
countered and little snow can be depended on, a light mulching 
of straw, buckwheat-hulls and other materials may be used. 

References 

Hartley, Carl. The blights of coniferous nursery stock. U. S. Dept. 

Agr. Bui. 44: 1-21. 1913. 
Hedgeock, G. G. Notes on some diseases of trees in our national 

forests. III. Phytopathology 3: 111-114. 1913. 
Hartley, Carl. Notes on winterkilling of forest trees. Forest Club 

(Univ. Nebraska) Ann. 4 : 39-50. 1912. 

FrEEZ ING-TO-D E ATH 

Caused by low temperatures 

The most common type of low temperature injury to plants 
is the direct killing of the susceptible parts. A part of the 
water in the plant is frozen when temperatures below the freez- 
ing-point are reached, and more and more water is withdrawn 
from the cells when the temperature becomes lower. The 
frozen water occurs as ice crystals which are mainly found in 
the intercellular spaces, but may be within the cells if the freez- 
ing occurs rapidl}'. Freezing-to-death has been frequently 
noticed and discussed for centuries, even before the internal 
structures of plants were understood. It was also early noted 
that the formation of ice crystals within the plant always 
accompanied freezing-to-death. The accepted and seemingly 
logical explanation of the cause of the death of the plant was 
that the plant-cells were ruptured, or otherwise mechanically 
destroyed during the formation of the ice crystals. This 
explanation is totally incorrect, however, although the exact 
physiological effect on the plant which results in death is as 
yet undetermined. 



SEEDLING DISEASES AND INJURIES 13 

Sy7J}2)toms. 

When plants suffer from low temperatures and ice crystals 
are formed within the tissues, the fii-st noticeable effect in the 
foliage is a wilted or flaccid appearance. The affected tissues 
have a general water-soaked character as soon as the plants 
are thawed. When the tissues of the buds and stems of plants 
are killed by ice formation, no evidence of the injury may be 
seen immediately after thawing. Later, however, affected 
parts show the water-soaked and browning symptoms. The 
cells adjacent to the tissues killed remain healthy and there 
is no enlargement of the lesion. 

Cause. 

As stated above, the death of plant-cells due to low tem- 
peratures is not a result of mechanical action in the process of 
ice formation. Nor is the injury due to the rate of thawing, 
as was long supposed. Carefully planned investigations on 
this subject have shown that death results when a certain tem- 
perature is reached. The critical temperature at which death 
results varies for different kinds of plants and the various parts 
of the same plant. The injury is due to some physiological 
effect of the taking of the water from the cell and changing it 
into ice. The injury has been ascribed, by various investi- 
gators, to the precipitation of the proteids in the cells, the 
drying of the plasma-membrane, the plasmolysis of the nuclei 
and to various other effects. It is known that various tissues 
of the same plant will withstand different critical temperatures, 
that plants differ widely in their resistance to low temperature 
injury, and that the previous treatment of a given plant may 
make it more resistant or more susceptible to a given degree 
of temperature. Previous exposure of the plant to temperature 
just above the killing point makes it more resistant, while 
lowering the temperature rapidly causes the plant to succumb 
at a temperature higher than the usual critical temperature for 



14 . MANUAL OF TREE DISEASES 

that plant. The stem- and root-tissues develop added resist- 
ance to low tempe^tures if they mature properly in the autumn. 
The exact nature of this maturing process is not understood, 
but growth must ceas5' and the tissues must pass slowly into 
the dormant stage. If the plant passes rapidly from the active 
vegetative condition into dormancy, the tissues are killed at a 
much higher temperature. The process of maturing in small 
seedlings is relatively much more rapid than in large trees. The 
roots are more liable to injury in the case of seedlings because 
they cease growth last and mature later than the aerial parts. 
They are also subject to injury because the feeding root-tips and 
tenderest rootlets are close to the surface of the soil. For a 
further discussion of freezing-to-death in older trees, see page 47. 
In the case of early or fall frosts, a sudden drop of temperature 
below 32° Fahr. may cause injury. Broad-leaf trees are more 
susceptible to - early frost-injury than conifers. Injury to 
seedlings may result in the spring from late frosts. Tempera- 
tures a little above 32° Fahr. may cause serious damage ow- 
ing to the extreme susceptibility of the new tissue. 

Control. 

High ground should be selected for the site for the seed- and 
transplant-beds in regions where low temperatures are common. 
At the same time, where sandy soil and danger from sun-scorch 
may be encountered, a site which will avoid both high and low 
spots should be selected. Early in the autumn only slight 
care should be given the beds since the trees should be allowed 
to cease growth and enter the dormant condition. Loose 
mulches advised under winter-drying (see page 11) will pro- 
tect the plants to some degree against freezing-to-death, es- 
pecially by keeping the temperature more uniform and de- 
creasing the rapidit}^ of temperature changes. The mulch 
should be allowed to remain on the beds as long as is safe in 
the spring in order to retard the beginning of growth. 



SEEDLING DISEASES AND INJURIES 15 

References on Freezing-to-Death 

Chandler, W. H. The killing of plant tissue by low temperature. 
Missouri Agr. Exp. Sta. Research Bui. .8 : 141-309. 1913. 

Zon, R. G. Effects of frost upon forest vegetation. Forestry Quar- 
terly 2 : 14-21. 1903. 

Hartig, R. Injuries due to atmospheric influences and fire. In 
Text-book of the diseases of trees, pp. 282-304, figs. 157-159. 
1894. 

Metcalf, H. Diseases of ornamental trees. U. S. Dept. Agr. Year- 
book 1907 : 483-494, pis. 58-60, fig. 52. 1908. 

Galloway, B. T., and Woods, A. F. Diseases of shade and ornamental 
trees. U. S. Dept. Agr. Yearbook 1896 : 237-254, figs. 53-57. 
1897. 

Smothering-Disease 

Caused by Thelephora laciniata Fries 

This disease is common and often destructive in seed-beds of 
spruce, fir and pine. It may, however, occur on trees of any 
species. The myceHum of the causal fungus does not enter 
and establish a parasitic relation with the living plant. It 
grows in the soil and uses decaying vegetable matter as food. 
A moist and continually humid atmosphere is necessary to 
furnish ideal conditions for the destructive development of 
this fungus. When the trees are planted thickly, this fungus 
produces an abundant growth of mycelium which adheres to 
the trees as confluent, incrusting, leathery la^'ers. It may 
ascend to a height of six or eight inches and encompass the 
trees. At frequent intervals, more or less horizontal shelves 
project from the fungous layers attached to the seedlings. 
These shelves may be narrow and coarsely toothed or broad 
and rosette-like with a lacerated margin. In its active vege- 
tative condition, the upper surface of the shelf is finely hairy 
and a rich dark brown with lighter zones of color. When old 
and somewhat dried, the entire fungous mass adhering to the 
trees becomes shrunken and a dirty dark brown. 



16 MANUAL OF TREE DISEASES 

The trees may be enveloped for only an inch or two above 
the soil with no considerable damage resulting, while at other 
times the entire plants or such a large part of their leaf- 
surface is covered that the trees die. The projecting shelves 
and the incrusting layers developed over the trees are the 
fruiting-structures of the fungus. The under and outer sur- 
face of the fungous layers is smooth and covered with branches 
of the mycelium which form spores at their tips. These spores 
are snapped off when mature and are distributed by the wind. 
In the seed-bed, however, the mycelium grows rapidl}'^ through 
the soil and thus distributes the fungus over large areas without 
the necessity of spore dissemination. 

When injury from the smothering fungus occurs, it is advis- 
able to remove the affected plants and those just adjacent, by 
lifting the soil containing them with a spade. Merely pulling 
the trees will leave the vegetative portion of the fungus in the 
soil where it can continue to spread. When the afl'ected 
plants are removed, measures should also be taken to reduce 
the soil and atmospheric moisture in the beds, by draining off 
excessive soil-water and removing any structures which shade 
the beds. These measures must be limited, however, so as 
not to predispose the plants to sun-scorch (see page 9) . Thin- 
ning the seedlings may be advisable under conditions in which 
the moisture factor cannot be otherwise easily controlled. 

References 

Hartig, R. Pseudo-parasites. In Text-book of the diseases of trees, 
pp. 35-36, fig. 8. 1894. 

Freeman, E. M. The smothering fungus of seedlings. In Minne- 
sota plant diseases, pp. 243-244. 1905. 



CHAPTER II 
LEAF DISEASES AND INJURIES 

The diseases and injuries of leaves common, in varying 
degrees, to all kinds of trees are due mainly to three general 
causes : extremes of moisture and temperature, atmospheric 
impurities, and an improper or impaired supply of raw materials 
and water. Of these, the extremes of moisture and temperature 
are the most important, especially when the trees are under 
normal conditions of growth. 

Conifers which keep their leaves throughout the winter may 
be injured by winter-drying as described under seedling diseases 
(see page 11). Freezing-to-death may cause destruction of the 
newly formed twigs and unfolding leaves of both conifers and 
deciduous trees when late frosts occur in the spring. Trees of all 
kinds often suffer severely from protracted drought periods 
because of the lack of sufficient soil-water. The scorching of 
the leaves occurs most commonly when dry hot winds cause 
excessive transpiration, as in the sun-scorch of seedlings (see 
page 9). The severity of such injuries depends largely on 
the natural requirements of the species and how well adapted a 
given tree is to its surroundings. Certain types of soils, the 
nature and direction of the slope and other such factors may 
predispose certain trees to winter-drying, late frost-injury or 
sun-scorch when other kinds of trees would not suffer. 

The injuries due to temperature and its important accompany- 
ing effect on transpiration are peculiar to extremes in weather 
conditions and usually seen after them. The causes of such 
injuries must be considered with the symptoms for a correct 
c 17 



18 MANUAL OF TREE DISEASES 

diagnosis of the trouble, since usually no determinative symp- 
toms are present. The ultimate factor of importance in most 
cases is an insufficient supply of water available to com- 
pensate for the loss by transpiration. Conditions bringing 
about such injuries may occur at any time of year when the 
leaves are on the tree. 

Atmospheric impurities are mostly injurious in and near 
cities where gases of various kinds are allowed to escape with- 
out restriction. Soot from ordinary coal-smoke may cause 
damage if quantities of it are continually falling on trees. 

The more abnormal the surroundings in w^hich trees are 
placed, the more important and common become the injuries 
due to faulty nutrition. The symptoms of malnutrition, in- 
dependent of other causes, are generally poor growth and the 
chlorosis or yellowing of the leaves. In addition to these types 
of injury which show prominently in the leaves, any diseased 
condition of the roots, trunk or branches which interferes 
with the necessary conducting of food materials to the leaves 
results in injury to the leaves. Consequently .in diagnosing 
leaf-injury, the leaves alone should not be examined but the 
condition of the branches, trunk and roots should be studied 
to see whether they show the primary symptoms. The 
diseases of leaves caused by specific pathogenes will be found 
discussed under the kind of tree attacked. 

Winter-Drying 

Caused by simultaneous low soil temperatures and high air tem- 
peratures 

Conifers which retain their foliage throughout the winter 
frequently suffer injury to the leaves of a part or all of the 
tree due to drying. After severe winters, trees may be found 
in exposed places which have been killed outright. The injury 
is very conspicuous and where generally prevalent it causes 



LEAF DISEASES AND INJURIES 19 

much alarm and is usually called blight. The true cause is 
often not known and a rapid spread of the trouble is expected. 
As explained under seedling diseases (see page 11), winter- 
drying is similar to sun-scorch or drought-injury, both in symp- 
toms and cause. Usually the leaves on the exposed side of the 
tree are first affected. Small trees with shallow root systems 
are often killed outright. In the case of older trees, only the 
leaves on scattered twigs or on the branches on the exposed 
side of the tree are affected. 

Symptoms. 

The affected leaves wither and die in late winter or early 
spring. Later the dead needles assume a red-browil color and 
the affected trees appear as if scorched by fire. Later in the 
summer the dead leaves and affected twigs may be shed. 
Adventitious buds are produced, from which a new crop of 
leaves develops in the autumn. 

Cause. 

Winter-drying is caused by the rapid loss of water from the 
leaves at a time when the water in the soil is frozen and is not 
available to the plant. Strong winds, when the air temperature 
is either high or low, cause the leaves on the exposed side of the 
tree to lose water to such an extent that the tissues wilt and 
die. The factors determining the extent of damage by winter- 
drying are : age of the tree and depth of roots in the soil, 
exposure to prevailing winds, temperature of the air, depth to 
which the soil-water is frozen, duration of strong winds blowing 
from a given direction and the frequency of reoccurrence of a 
combination of conditions favorable to winter-drying. Numer- 
ous semi-saprophytic fungi develop on the dead leaves, and 
thus give the impression, later in the season, that a destructive 
leaf-blight fungus has caused the damage. An easy way to 
determine whether injury to conifers noticed in the spring is 



20 MANUAL OF TREE DISEASES 

due to winter-drying or to fungous attack is to note carefully 
the needles affected on a few trees and then watch the trees 
throughout the season. If no further spread of the trouble is 
apparent during the summer, one may usually be assured that 
the damage was due to temperature conditions and not to 
leaf-parasites. 

Control. 

Little can be done to protect trees from winter-drying. In 
the case of ornamental conifers, it should be remembered 
that this trouble is common in places exposed to the wind 
and that young trees with shallow root systems are most 
susceptible. Mulching the soil around small trees may be 
advisable during winters when there is little snow on the 
ground. 

References 

Stone, G. E. Winter-injuries, drought, sun-scorch, and bronzing of 

leaves. In Shade trees, characteristics, adaptation, diseases 

and care. Massachusetts Agr. Exp. Sta. Bui. 170 : 199-212. 

1916. 
Morse, W. J. Winter injury of the white pine in 1908. In Notes 

on plant diseases in 1908. Maine Agr. Exp. Sta. Bui. 164 : 21- 

28, fig. 4. 1909. 
Hedgcock, G. G. Notes on some diseases of trees in our national 

forests. III. Phytopathology 3: 111-114. 1913. 
Spaulding, Perley. The present status of the white-pine blights. 

U. S. Dept. Agr. Bur. PL Ind. Circ. 35 : 1-12. 1909. 
Brooks, Charles. Pine blight. In Report of the Department of 

Botany. New Hampshire Agr. Exp. Sta. Ann. Rept. 19-20 : 

370-371. 1908. 
Hartley, Carl P. Notes on winterkilling of forest trees. Forest 

Club (Univ. Nebraska) Ann. 4 : 39-50. 1912. 
Galloway, B. T., and Woods, A. F. Desiccation, or drying out, and 

low temperatures. In Diseases of shade and ornamental trees. 

U. S. Dept. Agr. Yearbook 1896 : 243-246. 1897. 
Metcalf, Haven. Drying out. Effects of cold. In Diseases of 

ornamental trees. U. S. Dept. Agr. Yearbook 1907 : 486-487. 

1908. 



LEAF DISEASES AND INJURIES 21 

Late Frost-Injury 

Caused by low temperatures in the spring 

Low temperatures in the spring, after new growth has 
started, often result in what is cammonly known as late frost- 
injury. This type of injury is especially noted on conifers. 
The young growing tips of the branches, with the newly unfolded 
succulent leaves, wilt, die and turn brown. Sycamores and 
other deciduous trees which start their growth early also are 
often injured by bw temperatures in the spring. Li the case 
of the sycamore, the symptoms of late frost-injury and the 
anthracnose disease (see page 333) are often confused. The 
injury caused by late frosts is due directly to the freezing-to- 
death of the susceptible succulent growth. The tissues of the 
growing tips of the twig and the young unfolding leaves are the 
most susceptible of any of the tissues of the tree. Only a 
very slight fall of temperature below the freezing point is 
sufficient to cause the w^ithdrawal of enough water to result in 
death. For a more detailed description of the effects of low 
temperatures in causing freezing-to-death, see page 12. 

Lijury from late frost usually occurs on south slopes and in 
badly drained hollows known as frost-pockets. By planting 
susceptible species in locations usually free from frost and not 
exposed to the direct rays of the sun, a large part of the injury 
caused by late freezing may be avoided. Other methods of 
retarding the growth in the spring will also furnish some pro- 
tection. 

References 

Schrenk, Herman von. On frost injuries to sycamore buds. Mis- 
souri Bot. Garden Ann. Kept. 18 : 81-83, pi. 7. 1907. 

Morse, W. J. Winter injury of the white pine in 1908. In Notes on 
plant diseases in 1908. Maine Agr. Exp. Sta. Bui. 164 : 21-28, 
fig. 4. 1909. 



22 MANUAL OF TREE DISEASES 

Drought-Injury and Sun-Scorch 

Caused by high temperatures and dry soils 

In midsummer the foliage of many kinds of trees often ap- 
pears scorched. Pines and maples are commonly affected. The 
leaves of one side or of the entire tree may wither and turn 
brown. In general, this type of summer injury is similar to 
winter-drying (see page 18). The effects are the same and the 
causes similar. In winter-drying of conifers, a greater amount 
of water is lost than can be replaced because the ground-water 
is frozen. In the case of drought-injury and sun-scorch, water 
is lost from the leaves in quantities that cannot be replaced 
because of many conditions, such as : diseased or injured roots, 
a low water-table due to continued drought, or naturally dry 
and sandy soil. The injury usually occurs on the exposed 
side of the tree and commonly follows periods of hot dry winds. 
The sun-scorch of maple leaves has been found to follow imme- 
diately after an hour's exposure to high winds on hot days. 

In the case of conifers, the needles of the affected parts of the 
tree turn uniformly brown. With deciduous trees, large or small 
spots may be killed, leaving the remainder of the blade healthy 
and green. Usually the edge of the leaf, or the portion midway 
between the main veins, suffers first. Then if the drought con- 
ditions continue, the entire leaf may be killed and turn brown. 
The bronzed appearance of maple leaves commonly seen is 
typical of sun-scorch injury. Although, as stated above, sun- 
scorch following drought conditions or exposure to hot drying 
winds is usually found to be due to damaged root systems or 
dry soil, it sometimes happens that trees not so predisposed 
suffer merely from the effects of rapid transpiration. 

Reference 

Stone, G. E. Sun scorch and bronzing of leaves. In Shade trees, 
characteristics, adaptation, diseases and care. Massachusetts 
Agr. Exp. Sta. Bui. 170:210-212. 1916. 



LEAF DISEASES AND INJURIES 23 

Smoke- and Gas-Injury 

Caused by the products of incomplete combustion of coal 

Conspicuous injury to vegetation is noticeable around indus- 
trial centers where smoke and invisible poisonous gases are 
discharged into the air from chimneys. The manufacturing 
plants, large and small, office buildings, apartments, private 
residences, railroad locomotives, smelters, furnaces, kilns, and 
the like, are sources of smoke and gases, which in nearly every 
city or industrial center cause the death of certain species of 
plants, and chronic injury to other species for miles around. 
The topography of the coimtry surrounding the source of smoke 
and gas determines the distribution and extent of the injury. 
Prevailing winds and natural air currents, caused by hills and 
valleys, may result in but little damage at the source of the smoke 
and cause severe damage at a distance where the smoke settles. 
The zones of acute injury are readily traceable by the remains 
of trees and other plants killed by the fumes. If the produc- 
tion of poisonous fumes has been continued over a long period, 
the last vestige of plant life may have disappeared. This is 
especially true where fogs are common, which cause the fumes 
to be held in concentrated form over the immediate locality. 
When the source of smoke is in a valley, more injury may 
result just beyond the brow of the surrounding hills than imme- 
diately adjoining the source. The determination of the amount 
of damage caused by chronic injury some distance away from the 
source of smoke is sometimes difficult. IMuch of the trouble 
in encouraging normal tree growth in the cities is traceable to 
chronic injury by smoke and gases. In the open country, away 
from the other pathologic factors which are met with in the 
cities, the effects of acute injury have been found to extend for a 
distance of ten to fifteen miles from the source of smoke and 
gases, and the chronic injury to a much greater distance, some- 
times probably fifty or one hundred miles. 



24 MANUAL OF TREE DISEASES 

Trees vary greatly in their susceptibility to the poisonous 
substances in smoke. Conifers are more susceptible than decid- 
uous trees. The following order, from most susceptible to less 
susceptible, is reported by one writer: Alpine fir, Douglas 
fir, lodge-pole pine, western yellow pine, limber pine, Rock}^ 
INIountain juniper and dwarf juniper. In like manner the same 
writer reports the deciduous trees in order of least to greater 
resistance, thus : white elm, sycamore, locust, yellow poplar, 
Cottonwood, black gum, dogwood, red maple and white oak. 
In Des INIoines, Iowa, the willows and cottonwoods were found 
to be the most resistant trees. Also in that city the following 
deciduous trees were more resistant than pines : locust, white 
elm, ash, sycamore, silver maple, bur oak, white oak, red oak 
and box-elder. 

Symptoms. 

The symptoms of smoke- and gas-injury are variable ac- 
cording to whether the injury is acute or chronic and accord- 
ing to the species and age of the tree. When smoke is dense, 
more damage may apparently come from the coating of soot 
formed on the leaves than from the gases accompanying the 
smoke. In such cases the foliage is covered with the tar-like 
coating of soot and the leaves appear sickly and dwarfed. 
The tree as a whole is usually scrawny and makes but little 
growth each year. When the injury is more acute, and 
apparently due to the poisonous gases emitted along with the 
smoke, the leaves turn brown in spots and die. In the case 
of coniferous trees, the needles turn brown from the tip. 
Deciduous leaves usually appear as if sun-scorched, the portion 
of the leaf between the main veins turning brown first. In 
general, trees exposed to smoke have much smaller leaves than 
normal trees and often the leaves are crumpled. The killing 
of part of the foliage and the dwarfing and twisting of other 
leaves cause a greatly reduced leaf-surface for the manufacture 



LEAF DISEASES AND INJURIES 25 

of food, and consequently the whole tree suifers. Diminished 
growth, both in width of the annual ring and in length of the 
twigs, is a general symptom resulting from the direct injury 
to the leaves. Some writers believe that the gradual accumula- 
tion of the poisonous products in smoke, lodging in the soil, 
may have a detrimental effect on the trees. Some indication 
as to whether or not smoke is causing damage in a given locality 
may be determined by observing the presence or absence of 
lichens and the common green Pleurococcus which normally 
grow on the north sides of trees and posts. These plants are 
very susceptible to smoke-injury and will not appear where 
smoke is present. The common garden bean is one of the most 
susceptible of annuals and the behavior of this plant maybe 
taken as an indication of possible smoke-damage. 

Cause. 

The toxic property of smoke, and the accompanying invisible 
gases which issue with it from chimneys, is due to several 
substances, the most important of which is sulfur-dioxide. 
All coal contains some sulfur and when burned this escapes 
as a sulfur-dioxide gas. This gas is heavy and accumulates 
in the lower strata of the air. On further oxidation and 
contact with water, it dissolves and forms sulfuric acid which is 
corrosive and toxic to the living cells of the leaves. The 
cumulative effect of small amounts of sulfuric acid is to produce 
the burning symptoms noticed in acute injury, and cause the 
stunted and defcrmed foliage in more resistant plants. 

Soot and ashes falling on foliage also carry with them a certain 
amount of sulfin-ic acid. Soot itself causes added injury by 
accumulating as a tarry coating on the leaves and thus diminish- 
ing their photosynthetic power. The particles of soot may 
also clog the stcmates of the leaf and interfere with the normal 
exchange of gases necessary for starch formation. The am )unt 
of soot falling where smoke is abundant is enormous. In the 



26 MANUAL OF TREE DISEASES 

vicinity of Indianapolis, Indiana, it was computed that 1200 
tons of soot to the square mile were deposited in a year, which 
means ten and a quarter pounds to the acre every day. 

Other toxic substances which may accompany smoke are 
carbon-monoxide, acetylene, ethylene, arsenic and various 
toxic organic compounds found in the particles of tar accom- 
panying soot. The action of all these substances, where they 
accumulate in the soil, may cause direct or indirect injury to 
plants. It is thought that the elimination of the lower forms 
of plant and animal life in the soil may be the most important 
injurious factor, although the substances may be directly 
responsible for damage to growing trees by being taken in 
through the roots into the sap of the tree. 

Control. 

The prevention of smoke-injury is largely outside the power 
of the individual. However, it should not be difficult for an 
energetic community to secure relief from smoke conditions by 
establishing some sort of city control of the smoke nuisance. 
When the total elimination of smoke cannot be accomplished, 
smoke-resistant trees should be planted where conditions are 
worst. A careful study of the condition of those trees which 
remain in the vicinity of the source of the smoke will show what 
species should be chosen for replanting. 

References 

Bakke, A. L. The effect of city smoke on vegetation. Iowa Agr. 
Exp. Sta. Bui. 145: 383-409, figs. 1-22, map 1. 1913. 

Stone, G. E. Effects of atmospheric gases on vegetation. In Shade 
trees, characteristics, adaptation, diseases and care. Massa- 
chusetts Agr. Exp. Sta. Bui. 170 : 228-232. 1916. 

Buckhout, W. A. The effect of smoke and gas upon vegetation. Penn- 
sylvania Agr. Exp. Sta. Ann. Kept. 1900-1901 : 297-324. 1902. 

Clevenger, J. F. The effect of the soot in smoke on vegetation. 
Mellon Inst. Indus. Res. and School Spec. Indus. Bui. 7 : 1-26, 
pis. 1-8, figs. 1-2. 1913. 



LEAF DISEASES AND INJURIES 27 

Hajrwood, J. K. Injury to vegetation by smelter fumes. U. S. 

Dept. Agr. Bur. Chem. Bui. 89 : 1-23, pis. 1-6, fig. 1. 1905. 
Chivers, A. H. The injurious effects of tarvia fumes on vegetation. 

Phytopathology 7 : 32-36. 1917. 
Haywood, J. K. Injury to vegetation and animal life by smelter 

wastes. U. S. Dept. Agr. Bur. Chem. Bui. 113: 1-40, pis. 1-8. 

1908. 
Hedgcoek, G. G. Injury by smelter smoke in southeastern Tennessee. 

Jour. Washington (D. C.) Acad. Sci. 4: 70-71. 1914. 
Crowther, C, and Ruston, A. G. The nature, distribution and effects 

upon vegetation of atmospheric impurities in and near an in- 
dustrial town. Jour. Agr. Sci. 4: 25-55, figs. 1-3. 1911. 
Gatin, C. L. Die gegen die Abnutzung und den Stab der Strassen 

angewendeten Verfalu-en und ihre Wirkung auf die Vegetation. 

Zeitschr. f. Pflanzenkr. 22 : 193-204. 1912. 
McClelland, E. H. Bibliography of smoke and smoke prevention. 

Mellon Inst. Indus. Res. and School Spec. (Indus. Bui. 2 : 1-164, 

1913. 

Leaf-Spots 

Caused by various species of fungi 

There are many leaf-spots of all kinds of deciduous trees. A 
few of the most common ones are briefly described under the 
trees on which they occur (see index). The larger part of these 
diseases, however, have not been studied and the fungi that 
cause them are only imperfectly known. A general under- 
standing of the nature of these diseases will suffice in most 
cases for controlling them. Leaf-spots are mainly important 
only when defoliation results. 

Symptoms. 

Leaf-spot diseases are characterized by the formation of dead 
areas in the tissue of the leaf. These areas may be small or 
large and round, angular or irregular. The color of the dead 
tissues varies from yellowish to all shades of brown and almost 
black. Zones of various shades of the same colors may occur in 
the spot. The dead tissue often becomes broken and falls out, 
leaving ragged holes. Sometimes when small round dead areas 



28 MANUAL OF TREE DISEASES 

result, the affected tissue falls out entirely and the effect is 
known as shot-hole. When the spots become numerous the 
leaves may be killed and the tree is more or less defoliated. 

Various types of fruiting-bodies, of the fungi causing leaf- 
spots, are developed on the dead tissue. These structures 
appear to the unaided eye as minute brown or black dots 
scattered over the area or grouped in clusters near the center of 
the spot. Spores are produced in or on these structures. 

Cau^e. 

Leaf-spots are caused by many species of fungi, usually of 
the genera Phyllosticta, Septoria, Cylindrosporium, Cercospora, 
Marssonia and Gloeosporium. These genera represent groups 
in which the leaf-spot fungi are placed according to the micro- 
scopic characters of the fruiting-bodies and the spores, which are 
formed on the spots. The fruiting-bodies are simple inclosures 
(pycnidia) or spore-bearing layers of mycelium (acervuli). 
Because of the simplicity and variability of the structures, 
these fungi have been given numerous names. The confusion 
in classification has caused several names to be applied to the 
same fungus on the same tree and on different kinds of trees. 
In addition to the fruiting-structures mentioned above, the 
leaf-spot fungi in many cases develop perithecia and ascospores 
in the dead leaves on the ground during the autumn and winter. 

Following is a list of parasitic fungi which have been described 
as causing leaf-spots. In some cases more recent investigations 
have proved that several of the names are synonymous. These 
are indicated when known : — 

Alder 

Cylindrosporium vermiforme Davis 
Septoria alni Saec. 
Septoria alnicola Cooke 
Septoria alnifolia E. and E. 
Septoria maculans B. and C. 

= Rhabdospora maculans (B. and C.) Saec. 



LEAF DISEASES AND INJURIES 29 

Ash 

Cercospora fraxinites E. and E. 
Cercosporella trichophila Davis 
Cylindrosporium viridis E. and E. 
Glceosporium aridum El. and Hoi. 
Gloeosporium fraxineum Peek 
Gloeosporium fraxini Harkness 
Marssonia fraxini El. and Davis 
Phyllosticta fi axinicola Curr. 
Phyllosticta viridis El. and Kel. 
Piggotia fraxini B. and C 
Ramularia fraxinea Davis 
Septoria Besseyi Peck 
Septoria fraxini Desm. 
Septoria leucostroma E. and E. 
Septoria submaculata Winter 
Basswood 

Cercospora microsora Sace. 
Cercospora tiliw Peck, see page 102. 
Gloeosporium tilice udem. 
Phyllosticta stictica B. and C. 
Phyllosticta tilia: Sacc. and Speg. 
Beech 

Gloeosporium fagi (Desm.) E. and E. 

Gloeosporium fagi americanum (Desm. and Rob.) E. and E. 
Phyllosticta fagicola E. and M. 
Birch 

Cylindrosporium betulce Davis 
Gloeosporium, betularum E. and M. 
Septoria betulicola Peck 

= Septoria betulce (Lib.) West 
Septoria microsperma Peck 
Buckeye 

Glceosporium carpogemim Cooke 

Guignardia cesculi (Peck) Stewart, see page 118. 

= Lcestadia cesculi Peck 

= Phyllosticta cesculi E. and M. 

= Phyllosticta cesculicola Sacc. 

= Phyllosticta- pavia; Desm. 

= Phyllosticta sphceropsoidea Ellis 
Butternut 

Ascochyfa juglandis Boltsh. 
Cercospora juglandis K. and Schw. 
Gnomonia leptostyla (Fr.) Ces. and De Not. 

= Marssonia juglandis (Lib.) P. Magn. 



30 MANUAL OF TREE DISEASES 

Catalpa 

Cercospora catalpcB Winter 

Macrosporium catalpce E. and M. 

Phyllosticta catalpce E. and M. 
Chestnut 

Marssonia ochroleuca B. and C. 

= Cryptosporium epiphyllum E. and E. 

= Cylindrosporium castanicolum (Desm.) Berl. 

= Gloeosporium ochroleucum B. and C. 

Monochcetia Desmazierii Saec, see page 139. 

Phyllosticta cantanicola E. and E. 

Phyllosticta castanece E. and E. 

Phyllosticta fusispora E. and E. 

Septoria ochroleuca B. and C. 
Elm 

Cylindrosporium tenuisporum Heald and Wolf 

Cylindrosporium ulmicolum E. and E. 

Dothidella ulmea (Schw.) E. and E. . 

Dothidella ulmi (Duv.) Winter 

Gnomonia ulmea (Sacc.) Thiim., see page 152. 

Phleospora ulmi (Fries) Wallr. 

Phyllosticta confertissima E. and E. 

Phyllosticta erratica E. and E. 

Phyllosticta melaleuca E. and E. 

Phyllosticta ulmi West 
Hackberry 

Cylindrosporium celtidis Earle 

Cylindrosporium defoliatum Heald and Wolf 

Macrosporium antennoejorme B. and C. 

Phleospora celtidis El. and Martin 

Phyllosticta celtidis El. and Kel. 

Ramularia celtidis El. and Kel. 

Septoria celli-Gallce Gerard 

Septoria gigaspora E. and E. 
Hickory 

Gloeosporium carycB El. and Dearn. 
= Gnomonia caryce Wolf 

Marssonia juglandis (Lib.) Sacc. 

Phyllosticta caryce Peck 
Locust 

Cylindrosporium solitarium Heald and Wolf 
Maple 

Cercospora negundinis E. and E. 

Cylindrosporium negundinis E. and E. 

Gloeosporium cceris Cooke 



LEAF DISEASES AND INJURIES 31 

Gloeosporium apocrypium E. and E., see page 226. 

Gloeosporium negundinis E. and E. 

Gloeosporium saccharinum E. and E. 

Phyllosticta minima (B. and C.) E. and E., see page 226. 

= Phyllosticta acericola C. and E. 

= Phyllosticta tninutissima E. and E. 

= Phyllosticta negundinis Sacc. and Speg. 

= Phyllosticta saccharina E. and M. 
Rhyiisma accrinum Fries, see page 223. 
Rhytisma punctatum Fries, see page 225. 
Septoria acerella Sacc. 
Septoria acericola Desm. 
Septoria acerina Peck 
Septoria aceris B. and Br. 
Septoria marginata Heald and Wolf 
Septoria saccharina E. and E. 

= Ascochyta aceris Lib. 

= Cylindrosporium saccharinum E. and E. 

= Phleospora aceris (Lib.) Sacc. 
Septoria sallice Gerard 
Oak 

Ascochyta Quercus Sacc. and Speg. 

Gloeosporium nervisequum (Fckl.) Sacc, see page 237. 

Gloeosporium quercinum West 

Gloeosporium quernum Hark. 

Gloeosporium septorioides Sacc. 

Leptothyrium dryinum Sacc. 

Marssonia Martini (Sacc. and Ellis) P. Magn, 

= Gloeosporium Martini Sacc. and Ellis 
Marssonia Quercus Peck 

= Glceosporium Quercus Peck 
Pestalozzia flagellata Earle 
Phyllosticta agrifolia E. and E. 
Phyllosticta apiculata Sacc. and Syd. 
Phyllosticta livida E. and E. 
Phyllosticta ludoviciana E. and M. 
Phyllosticta phomiformis Sacc. 
Phyllosticta Quercus Sacc. and Speg. 
Phyllosticta Quercus-illicis Sacc. 
Phyllosticta Quercus-prini E. and E. 
Phyllosticta Quercus-ruhrce Gerard 
Phyllosticta tumoricola Peck 
Phyllosticta vesicatoria Thiim. 
Phyllosticta virens E. and E. 
Phyllosticta Wislizeni E. and E. 



32 MANUAL OF TREE DISEASES 

Rhytisnia erythrosporum B. and Cl. 
Septoria dtyina Cooke 
Sepioria neglccta Earle 
Septoria querceti Thlim. 
Septoria serpentaria E. and M. 
Poplar 

Marssonia castagnei (D. and M.) P. Magn. 

= Trochila populorum Desni. 
Marssonia populi (Lib.) Sace. 

= Glaosporium populi (Lib.) Mont, and Desm. 
Marssonia rhabdospora (E. and E.) Magn. 
Phylloslicta maculans E. and E. 
Septoria musiva Peck 

= Cylindrosporium oculatum E. and E. 

= Phylloslicta populina Sacc. 

= Septoria Candida (Fckl.) Sacc. 

= Septoria populi Desm. 

= Septoria salicina Peck 
Septoria populicola Peck 
Sycamore 

Gloeosporium nervisequum (Fckl.) Sacc, see page 333. 
Phleospora multi maculans Heald and Wolf 
Phylloslicta plalani Sace. and Speg. 
Septoria platanifolia Cooke 
Walnut 

Ascochyta juglandis Boltsh. 

Cylindrosporium juglandis Wolf. 

Marssonia juglandis (Lib.) P. Magn., see page 339. 

= Gnomonia leptostyla (Fr.) Ces. and De Not. 
Phleospora multimaculans Heald and Wolf 
Septoria juglandis B. and C. 

= Rhabdospora juglandis (Schw.) Sace. 
Willow 

Cercospora salicina E. and E. 
Glaosporium macidans Hark. 
Glceosporium salicis West 
Marssonia apicalis Davis 
Phylloslicta apicalis Davis 
Ramularia rosea (Fckl.) Sacc. 
Ramularia uredinis (Voss) Sace. 
Rhytisma salicinum Fries, see page 343. 
Septogloeum salicinum (Peck) Sace. 
Septoria albaniensis Thiim. 
Septoria salicina Peck 



LEAF DISEASES AND INJURIES 33 

In general the life history of these fungi is similar for all the 
species. The spores causing primary infection in the spring 
may come from two sources. The ascospores developed on the 
dead leaves are forcibly ejected into the air and are borne by 
the wind. Usually the leaves of the lower branches are most 
heavily infected by these spores. Also, if the mycelium of 
the fungus should be one which afi'ects the bark-tissues of the 
twigs, primary infection may result from spores produced in 
fruiting-bodies on the bark. During the spring and summer, 
the destructive spread of the fungi is due to the abundant 
spore-production in the fruiting-bodies on the dead areas of 
the leaves. 

Wet seasons are particularly favorable for epiphytotics of 
leaf-spot diseases. This is due to the fact that abundant 
mcisture is necessary to disseminate the spores and to induce 
germination. In this way several generations of spores are 
produced until the leaves are so generally affected that defolia- 
tion may result. 

Control of leaf-spots. 

In the forest no direct methods of control for leaf diseases 
are practicable. With shade and ornamental trees, however, the 
appearance of the tree or the protection from repeated defolia- 
tion, may warrant the expense necessary to control the fungus. 
All leaves which fall from affected trees should be raked together 
and burned in the autumn. If this is carefully done for some 
distance away from the trees, much of the primary infection 
will be avoided. In case the fungus also affects the twigs, 
all the dead and cankered twigs should be pruned off before the 
buds burst in the spring (see under control of leaf-blight and 
w^itches'-broom of sycamore, page 337). Even if these eradica- 
tion measures are taken, the fungus may appear, especially in 
wet seasons, by spreading from surrounding trees, or because 
a sufficient number of spores were available for primary infection 



34 MANUAL OF TREE DISEASES 

from bits of leaves or diseased twigs which were not burned. 
The eradication measures, therefore, should be supplemented 
by spraying or dusting, as the leaves unfold and grow to full 
size. For large trees, these measures are expensive and are not 
advised except under extraordinary circumstances. Directions 
for spraying and dusting will be found on page 357. 

Powdery Mildews 

Caused by fungi of the family Erysiphaceae 

The leaves and sometimes the twigs and fruits of many kinds 
of plants are attacked by the fungi of the family Erysiphacete, 
which cause powdery mildews. One or more of these powdery 
mildews attack the leaves of most kinds of deciduous trees in 
the United States. Two species of these fungi, MicrosphoBva 
alni and Phyllactinia corylea, occur generally throughout the 
country and may be expected on all kinds of broad-leaf trees. 
The following list of the powdery mildew fungi reported in this 
country on the different kinds of trees may be of interest, al- 
though without the aid of a microscope no definite characters 
are available for distinguishing one powdery mildew from 
another : — 

Alder 

Erysiphe aggregata (Peck) Farlow (on female catkins), see page 86. 

Microsphcera alni (Wallroth) Salmon 

Phyllactinia corylea Karsten 
Ash 

Phyllactinia corylea Karsten 
Basswood 

Uncinula Clintonii Peck, see page 101. 
Beech 

Microsphcera alni (Wallroth) Salmon 

Phyllactinia corylea Karsten 
Birch 

Microsphcera alni (Wallroth) Salmon 

Phyllactinia corylea Karsten 



LEAF DISEASES AND INJURIES 35 

Buckeye 

JJ ncinula jlexuosa Peek, see page 121. 
Butternut 

Microsphcera aim (Wallroth) Salmon 

Phyllactinia corylea Karsten 
Catalpa 

Microsphoera aim var. vaccinii (Schweinitz) Salmon 

Phyllactinia corylea Karsten 
Chestnut 

Microsphoera alni (Wallroth) Salmon 

Phyllactinia corylea Karsten 
Elm 

Microsphoera alni (Wallroth) Salmon, see page 153. 

Phyllactinia corylea Karsten, see page 153. 

Uncinula macrospora Peck, see page 153. 
Hackberry 

Sphoerotheca phytoptophila Kellerman and Swingle, see page 174. 

Uncinula parvula Cooke and Peck, see page 173. 

Uncinula polychoela (Berkeley and Curtis) Ellis, see page 173. 
Hickory 

Microsphoera alni (Wallroth) Salmon 
Honey locust 

Microsphoera alni (Wallroth) Salmon 
Maple 

Phyllactinia corylea Karsten, see page 227. 

Uncinula circinata Cooke and Peck, see page 227. 
Oak 

Erysiphe trina Harkness, see page 241. 

Microsphoera alni (Wallroth) Salmon, see page 241. 

Microsphoera alni var. extensa (Cooke and Peck) Salmon, see page 
241. 

Phyllactinia corylea Karsten, see page 241. 

Sphoerotheca lanestris Harkness, see page 243. 
Poplar 

Uncinula salicis (Fries) Winter, see page 300. 
Sycamore 

MicrosphfTra alni (Wallroth) Salmon 
Walnut 

Microsphrrra alni (Wallroth) Salmon 

Phyllactinia corylea Karsten 
Willow 

Phyllactinia corylea Karsten, see page 341. 

Uncinula salicis (Fries) Winter, see page 341. 
Yellow poplar 

Phyllactinia corylea Karsten 



36 MANUAL OF TREE DISEASES 

SymptoiJis of powdery mildews. 

Of the fifteen species or varieties of these fungi on trees in 
this country, all are confined to the upper or lower surface of 
leaves, except Sphcorotheca lanestris, causing the brown mildew 
of leaves and twigs of oak, Sphwrotheca phytoptophila, on buds, 
twigs and leaves of the witches'-brooms of hackberry, and 
Erysiphe aggregata on the fertile catkins of alders. In all of 
these species, also, the mycelium is white and appears powdery 
except that, with age, the mycelium of Sphcerotheca lanestris 
becomes brown, and that of Erysiphe aggregata somewhat 
yellowish. The mycelium of all the species is entirely super- 
ficial and is visible in mass to the unaided eye. Under cer- 
tain favorable conditions of growth, the mycelium becomes so 
abundant that definite white (or in some cases brown or yellow, 
as mentioned above) felts are formed. More often, however, 
the growth is not so plainly visible and the affected areas 
appear as blanched or slightly whitish and indefinite. In 
the early stages of development, the mycelium produces enor- 
mous numbers of white spores which cause the affected area 
to appear powdery. This character is the main diagnostic 
symptom for recognizing these mildews in the spring and 
summer. 

As the season advances, the powdery white mycelium becomes 
less apparent in most cases and only traces can be detected. 
However, during late summer and autumn when these characters 
become less distinct, many small yellowish, globose bodies just 
visible to the eye begin to appear on the affected part of the 
leaf. These bodies become dark brown or black and are the 
fruiting-bodies which contain ascospores. Except when very 
young succulent growth is attacked, no material damage is 
done to the leaves. Young growth, however, may be stunted 
in development, as when S. lanestris occurs on oak twigs and 
leaves (see page 243). 



LEAF DISEASES AND INJURIES 37 

Caiise. 

All the powdery mildew fungi belong to the same family and 
have similar life histories. The black fruiting-bodies contain- 
ing the spores over-winter on the fallen leaves. They crack 
open the next spring, forcibly liberating the ascospores which 
are caught up by the wind and are carried away to infect the new 
developing foliage. Infection is brought about by the asco- 
spores which lodge on leaves of the right kind of tree, if conditions 
of moisture and temperature are correct for germination. The 
germ tube penetrates the outer wall of an epidermal cell of the 
leaf and produces a thread of mycelium wdthin the cell. Food 
materials are thus obtained by the fungus and the mycelium 
branches out from the external part of the germ tube, and forms 
a richly branching growth over the surface of the leaf. Here 
and there short lateral branches, called haustoria or suckers, pen- 
etrate into other epidermal cells to obtain food. In this way the 
fungus develops until its growth is visible to the eye and some- 
times, from a single infection or by the intermingling of many 
individual infections, the mycelium may cover most of the leaf- 
surface. Numerous short erect branches are formed and from 
these are cut off large numbers of small spores which are so 
abundant that the thready character of the mycelium is masked, 
and the area appears powdery. These spores are disseminated 
by the wind and may start new infections. The mycelium 
and the spores, developed before the black fruiting-bodies ap- 
pear, are so nearly alike for all powdery mildew fungi that they 
cannot be distinguished one from another. The microscopic 
characters of the black fruiting-bodies (perithecia) and the 
asci and ascospores which they contain serve to classify the 
mildews into several genera and species within genera. 

Control. 

Powdery mildews are easily controlled, since the mycelium is 
external and can be kiUed by applying toxic substances in a 



38 MANUAL OF TREE DISEASES 

liquid or dust form. Gathering and burning the fallen leaves 
will reduce the amount of primary infection in the spring. 
During the summer, when It is desired to prevent the further 
development of these fungi, flowers of sulfur or preferably 
finely ground sulfur-flour may be dusted on the affected leaves. 
For large trees, blowers must be used which will produce a fog 
of the sulfur-dust that will settle all over the foliage. Lime- 
sulfur solution (1-50) with the addition of three pounds of 
iron-sulfate to each fifty gallons of the mixture is also effective. 
Bordeaux mixture and other copper mixtures are not advised. 
If possible, the application of sulfur-dust should be made in the 
early morning while the trees are still damp, and preferably at a 
time when weather conditions are to continue warm and dry. 
The fungicidal value of sulfur is much greater under such 
conditions. For fuller directions on spraying and dusting, see 
page 357. 

Reference 

Salmon, E. S. A monograph of the Erysiphaceae. Mem. Torrey 
Bot. Club 9 : 1-292, pis. 1-9. 1900. (Bibliography given.) 

Leaf-Cast of Conifers 

Caused by fungi of the genera Lophodermium, Hypoderma and 
Hypodermella 

Several similar diseases of pine, larch, fir, spruce and juniper 
are known under the general name of leaf -cast. Other names, 
such as leaf-browning, leaf-reddening and cracking-scurf, have 
been applied to these diseases. In Europe the leaf-cast diseases 
of conifers have often assumed the nature of epiphytotics and 
serious damage Is common in nurseries and in the forest. Before 
the cause of the leaf-cast diseases was known, they were con- 
fused with all types of leaf-browning of conifers. The Scotch 
pine is the most severely injured of the various conifers affected 
in Europe. In the United States the leaf-cast diseases have 



LEAF DISEASES AND INJURIES 39 

not assumed such general Importance and are only found de- 
structive to certain species in restricted areas. In California, 
white and Shasta red fir, lodge-pole, western yellow, and JefFrey 
pine are frequently affected by leaf-cast. In the Northwest, 
leaf-cast occurs destructively on western yellow and white pine 
and on western larch. In eastern United States, white pine 
and balsam fir are sometimes affected. 

Symptoms. 

The general symptoms of leaf-cast are similar in a way to 
sun-scorch and other injuries which cause the needles to die 
and turn reddish or brown. In leaf-cast, however, the first in- 
dication of the disease is the appearance of yellowish or brownish 
bands or spots on the needles. The needles do not suddenly 
turn brown at the tips or in their entirety as is the case when a 
lack of water causes the death of the needles. Also in leaf- 
cast, the needles of a single bundle or twig are usually not all 
affected simultaneously. After a needle shows the brown 
spots, it soon turns yellow or brown and may fall off. Some- 
times the twigs are affected and they are either stimulated to 
form witches'-brooms or are killed. 

The fruiting-bodies of the causal fungi appear as roundish or 
elongate black pustules on the surface of the affected leaves. 
The fruiting-bodies may not be formed until the leaves fall to 
the ground. When closely examined, a narrow line will be 
seen running lengthwise of the fruiting-body and dividing it 
into halves. In the spring the two halves break apart at this 
line and fold backward, exposing the spores. 

Cause. 

The leaf-cast diseases of conifers are caused by several species 
of fungi belonging to the closely related genera, Lophodermium, 
Hypoderma and Hypodermella. In this country the following 
species have been found to cause leaf-cast : — 



40 MANUAL OF TREE DISEASES 

On white and pitch pine and hemlock in eastern United States, — 
Hypoderma strobicola Tubeuf = Lophodermium brachyspoi-um Rostrup. 

On balsam fir in eastern United States, and wtdte and Shasta red 
fir in California, — Lophodermium nervisequum Fries. 

On western larch in the Northwest — Hypodermella laricis Tubeuf . 

On western yellow pine in the Northwest, — Hypodervia deformans 
Weir. 

On lodge-pole pine in California, — Hypoderma sp. 

On western yellow pine in California, — Lophodermium sp. 

To the unaided eye, the fruiting-bodies of these fungi are all 
similar. The roundish or elongate black raised pustules mature 
during the winter. With the coming of warm spring rains, the 
fruiting-body splits along the median cleavage line and the two 
valve-like halves are folded back. In this condition the layer 
of asci containing ascospores is exposed. The spores are shot 
into the air and are disseminated l)y the wind. If all the spores 
are not ejected the first time, subsequent rain periods will cause 
further spore-ejection. In this way the periods of infection 
may be distributed in dry climates over the entire growing 
season. Where rain periods are more frequent in the spring, 
most of the infection occurs in ]May and June and the supply 
of spores is exliausted. The needles of the current season 
only are affected in the case of some of the leaf-cast diseases, 
while in others the older needles are affected and the young 
needles remain healthy. The mycelium in some cases enters 
the twigs and may induce the formation of witches'-brooms, or 
the affected twig may be killed outright. 

Control of leaf-cast diseases. 

In the forest no measures of control are practicable. In 
nurseries the trees may be sprayed with bordeaux mixture. 
The mixture should be applied before the rain periods which 
cause the ejection of the spores. In order to avoid the expense 
of spraying for these diseases, nurseries should be located at a 
distance from coniferous forests and thus avoid chances of 
infection. 



LEAF DISEASES AND INJURIES 41 

For further details and references in literature concerning the 
leaf-cast diseases, see the discussions under pine diseases (pages 
270 and 271) and fir diseases (page 159). 

Sooty Molds 

Caused by fungi of the family PerisporiaeeaB 

The leaves of many trees are often covered with a 
black sooty coating in midsummer. No serious damage is 
done to the tree unless the growth on the leaves becomes so 
abundant that it interferes with the functions of the leaf by 
shutting out the sunlight. The fungi causing this type of growth 
on leaves are closely related to the powdery mildew fungi (see 
page 34). The mycelium of the sooty mold fungi is, however, 
dark colored and appears to the eye as black. As in the case of 
the powdery mildews, the mycelium is superficial. No feeding 
rootlets are sent into the leaf-tissue, however, as in the powdery 
mildews, and the fungi are therefore not parasitic. They 
obtain sufficient nourishment from sugary solutions that are 
exuded from the leaves. Sugary exudations are only formed 
on leaves under certain conditions, and when these are absent 
the sooty molds do not occur. When aphids are present, sooty 
molds find excellent conditions for developing. These fungi 
may be controlled by spraying, and the recommendations given 
for powdery mildews should be followed (see page 37) . 

Silver-Leaf 

Caused by Stereum purpureum Fries 

Although the disease known as silver-leaf or silver-blight 
has not been shown to be as widespread or destructive on forest- 
and shade-trees as it is on fruit-trees, nevertheless it is known to 
occur on ash, chestnut and others. As a disease of fruit-trees 



42 MANUAL OF TREE DISEASES 

and small-fruits, it has been studied in Europe since 1885 when 
it was first described in France. Apple, plum, peach, apricot, 
cherry, almond, currant, gooseberry and lilac are among the 
trees and smaller woody plants known to be affected. The stone- 
fruits are probably most seriously affected.' The disease is 
known at present in France, England, Germany, Canada, 
northeastern United States, South Africa and New Zealand, 
but probably has a much wider distribution. It has been 
noticed in the forest and on trees outside the forest in north- 
eastern United States and the adjacent regions of Canada. 

Symptoms. 

The leaves of affected limbs are at first paler in color and 
finally become milk-white, lead-colored or silvery. The green 
color is not entirely lost but is only faintly evident in the silvered 
areas. The disease shows in two distinct types depending on 
the part of the tree first attacked. Usually the first symptoms 
of silver-leaf are confined to a single twig, and then from year 
to year other twigs, large branches and finally the entire tree 
show the disease. Before the entire tree is diseased, however, 
the twigs first affected die and the fruiting-bodies of the causal 
fungus appear on them as small white and purplish encrusting 
patches. At other times the roots are infected first and large 
branches develop silvered leaves suddenly, and very soon the 
entire tree becomes diseased. On cutting into the branches 
which show silvered leaves, the wood will be found to be dark 
brown. The connection between these symptoms is explained 
in the discussion below. 

Cause. 

The cause of silver-leaf long remained a mystery, largely 
because many scientists thought without experimentation that 
it was due to simple physiological disturbances. However, 
it has been definitely proved that the fungus, Stereum pur- 



LEAF DISEASES AND INJURIES 43 

'pureum, which grows in the wood of the tree is the cause of the 
disease. Inoculations from pure cultures of this fungus made 
into the wood of roots, trunks and branches cause the develop- 
ment of typical silver-leaf. The fungus occurs as a common 
saprophyte everywhere and produces its fruiting-bodies on 
dead wood, stumps and brush of all kinds. Spores from the 
fruiting-bodies may cause infection of the exposed wood of 
healthy trees. Less often the roots of trees may be invaded by 
the mycelium. The mycelium grows in the heartwood, causing 
it to turn uniformly brown. When infection occurs in the wood 
of branches, the leaves just above the point of infection show 
silvering tiie next season and in three to six years the remainder 
of the foliage of the tree may become affected. When examined 
microscopically, the silvery appearance of the leaves is found to 
be due to the enlargement of the epidermal cells. This results 
in the loosening of the epidermis and the formation of an air- 
space between it and the palisade cells which contain the green 
coloring matter. The other cells of the leaf are only loosely 
held together and it is presumed that a ferment, produced by 
the fungous hyphee growing in the wood, is transported to the 
leaves and dissolves the cementing layer between the cells. The 
mycelium itself does not enter the leaves but is confined to the 
dark colored wood. Silvering never occurs without the pre- 
vious browning of the wood. When the branch dies, Stereum 
purpureum and other saprophytic fungi may soon develop their 
fruiting-bodies on it. 

Contrul of silver-leaf. 

Since the fungus causing silver-leaf is a wound parasite, some 
degree of protection may be afforded healthy trees by protecting 
wounds with dressings (see page 348) . Diseased limbs should be 
cut from affected trees to the extent that no parts showing the 
bi own discolored wood are left ; otherwise the fungus will pro- 
ceed in its growth into the trunk and out into other branches. 



44 MANUAL OF TREE DISEASES 

All dead wood, brush and stumps which may harbor this fungus 
and produce the fruiting-bodies should be removed and burned 
to eliminate the sources of spore-production. 

References 

Hesler, L. R., and Whetzel, H. H. Silver-leaf. In Manual of fruit 

diseases, pp. 368-373, fig. 108. 1917. 
Giissow, H. T. Der Milehglanz der Obstbaume. Zeitsehr. fur Pflanz- 

enkr. 22 : 385-401, pis. 5-6, fig. 1. 1912. 
Brooks, F. T. Silver-leaf disease. Jour. Agr. Sci. 4 : 133-144. 1911. 
Brooks, F. T. Silver-leaf disease (II). Jour. Agr. Sci. 5:288-308. 

1913. 



CHAPTER III 
BODY AND BRANCH DISEASES AND INJURIES 

Many diseases and injuries of the bark and wood 
are more or less common to all kinds of trees. Extremes 
of temperature, lightning, mistletoes, lichens and some species 
of fungi are some of the causal agents which affect trees in 
general. As in the case of the diseases and injuries common 
to the seedlings and leaves of many kinds of trees, the primary 
causal agents of the diseases affecting bark and wood are often 
difficult to determine. It is only by a careful analysis of the 
conditions surrounding the tree in question and by close ob- 
servation of other trees in the vicinity that clues can be ob- 
tained. Also, in such cases, the knowledge of similar tree 
troubles may be essential in determining the exact cause. 
Many of the diseases and injuries of the branches and trunk 
affect the appearance of the leaves before direct attention is 
called to the primary injury. 

In general, the presence or absence of fruiting-bodies 
of fungi on the bark is of but little value in determining 
whether or not the trouble is caused by a specific fungus. 
This is due to the fact that numerous species of fungi 
find excellent conditions for growth in dead bark and some 
species follow very closely any injuries to the bark. A 
trained pathologist must be closely observant to assert even 
tentatively that a fungus found on dead areas of bark is 
responsible for the lesion. The only sure way of proving 
the fungus to be the cause of disease is the usual procedure of 
isolating and growing the fungus in pure cultures and inoculat- 

45 



46 MANUAL OF TREE DISEASES 

ing it into healthy plants. Often, however, an active patho- 
gene shows characteristic parasitic tendencies, especially to the 
trained eye, which make diagnosis more certain. A comparison 
of the edge of a canker on chestnut caused by Endothia 
parasitica with that caused by winter-injury, lightning or 
mechanical agents will illustrate the general characteristics 
between an actively enlarging canker caused by parasitic 
fungus and an area of dead bark invaded by a saprophyte. 
From the outside such cankers may appear very similar, 
but on cutting into the margin of the cankered area the one 
caused by the active parasite shows a more or less gradual 
gradation between the color and organization of the tissues of 
the healthy light colored bark and the disorganized, usually 
brown-colored diseased bark. Usually also, the fine mats of 
mycelium can be seen advancing into uninjured and healthy 
bark-tissue. On the other hand, in the case of an area of bark 
killed by some other agent than an active parasite, the margin 
of the canker when cut into is usually definite and the distinc- 
tion in color and other characters between the healthy and dead 
bark-tissues readily proves that the lesion is not becoming 
larger, and that any saprophytic fungus present in the dead 
bark is not advancing into healthy tissue. 

In this chapter are discussed several of the most common 
diseases and injuries of trees. It should be remembered that 
the general health and appearance of the bark and wood of the 
tree depend naturally on the health and condition of the foliage 
on the one hand and the condition of the roots on the other. 
The stunted and dwarfed condition of trees, slow" annual growth, 
deformed crowns, stag-head, dead branches, irregular branching 
and sucker development are all signs of abnormal conditions 
either at the source of starch production in the leaves or in the 
food supply and general soil conditions around the roots. The 
most common causes of such general symptoms of abnormal 
growth shown by the branches or trunk are: (1) smoke-, 



BODY AND BRANCH DISEASES AND INJURIES 47 

gas- and soot-injury to the foliage ; (2) unbalanced relation 
between root and foliage system caused by cutting away sur- 
rounding trees, or by injudicious pruning and pollarding ; (3) un- 
balanced water supply in the soil, caused by the physical con- 
dition of the soil, or insufficient water reaching the roots due 
to pavements and sod ; (4) poisoning, due to natural or arti- 
ficial gas escaping into the soil ; (5) mal-nutrition, due to lack 
of certain essential food elements in soil or the over-balancing 
of the food supply by improper use of fertilizers, which causes 
toxic injury. JNIany of these tree troubles which are due to 
unbalanced physiological processes, improper soil, site and 
food supply, improper care in planting, pruning and the like, 
and the relation of trees to their neighbors are purposely omitted 
from discussion in this book. 

Freezing-to-Death of Twigs and Bark 

Caused by low temperatures 

Twig-blight due to freezing-to-death is common with certain 
kinds of trees. Trees such as ash, oak, spruce and others 
which cease twig growth early in the autumn and form ter- 
minal buds, are usually resistant to freezing-injury. The wood 
and bark of the twigs have sufficient time to mature and become 
resistant to low temperatures. If, however, due to exception- 
ally warm and moist conditions in the late autumn, growth is 
resumed, the twigs may be severely injured by early frosts. 
Other kinds of trees, such as basswood, sycamore and elm, 
which do not naturally cease twig growth early in the autumn, 
are injured frequently by freezing. The twigs of the locust and 
certain willows continue growing until late autumn and freeze 
back every year. 

The injuries of bark due to extremes of temperature are 
largely limited to those caused by freezing. Although condi- 
tions which cause temperature injuries to the leaves have a 



48 MANUAL OF TREE DISEASES 

general effect on the health and development of the branches, 
the injury is not directly noticeable, unless the tree is seriously 
damaged by such leaf troubles year after year. It was formerly 
thought that the characteristic cankers in the bark of trees 
associated with extremes of temperature were of two sorts, 
called respectively, sun-scald, when the drying-out effect of 
the sun's rays was the cause, and winter-injury or freezing-to- 
death, when areas of bark were killed by extremely low tem- 
peratures in winter. It is now held that a very large pro- 
portion of such cankers are due to freezing-to-death and that 
sun-scald cankers caused by extremes of heat in summer are 
rare. 

Cankers or dead areas of bark due to freezing often occur in 
crotches, on the south and southwest sides of the trunk, and 
around the base of the tree. Crotch-cankers are common and 
are thought to be due to the tissues at these places being 
more parenchymatous and much more slowly matured than 
the adjacent bark-tissues. Thus the bark at crotches is more 
susceptible to freezing-to-death, and injury occurs at a higher 
temperature than would cause injury to properly matured tissue. 
The cankered dead areas, often with the bark fallen away, on 
the south and southwest sides of the trunk are common in 
certain kiiids of trees, notably the Norway maple. The injury 
occurs in late winter when the sun's rays in the afternoon raise 
the temperature of the bark above the freezing point, to be 
followed at night by a temperature below freezing. The dif- 
ference in temperature between the north and south sides of 
a tree often amounts to as much as ten degrees. Several 
explanations can be offered to account for the injury : (1) with 
the daily rise in temperature new growth is started and the 
tissues formed are more susceptible to low temperatures at 
night ; (2) repeated thawing and freezing of the tissues de- 
crease their resistance to freezing ; (3) the rapid fall from a 
high to a low temperature causes the death of the tissue at a 



BODY AND BRANCH DISEASES AND INJURIES 49 

higher temperature than if the rate of fall was more gradual ; 
(4) the tensions set up in the bark and wood by the alternate 
increase and decrease of the temperature cause mechanical 
separation of the bark from the wood and this destroys the 
cambium region. The cankered areas commonly found at the 
base of the trunk are explained in the same way. Various 
species of saprophytic and semi-saprophytic fungi soon appear 
and produce their fruiting-bodies on the dead bark. The 
repeated attempts at callusing on the edge of the canker may 
fail, because the callus tissue, being largely parenchymatous, 
is susceptible to freezing-injury and is killed. 

To prevent wound parasites from gaining a foothold and 
causing further damage to the tree, surgical methods should 
be used and the wound protected. For the proper procedure 
in removing the dead bark and shaping the wound, see page 
351. As a dressing for such wounds it would be advisable to 
use pure white lead paint, renewing the dressing at least once 
every year. By using a white dressing instead of a black one, 
some added protection is afforded the callusing edges of the 
wound, since the sun's rays will not heat the bark to as high 
temperature. 

References 

Mix, A. J. Sun-scald of fruit trees, a type of winter injury. Cornell 

Univ. Agr. Exp. Sta. Bui. 382 : 235-284, pis. 18 and 'l9, figs. 60 

and 61. 1916. 
Chandler, W. H. The killing of plant tissue by low temperature. 

Missouri Agr. Exp. Sta. Research Bui. 8 : 141-309. 1913. 
Hartig, R. The action of frost. In Text-book of the diseases of 

trees, pp. 282-294, figs. 157-158. 1894. 
Zon, R. G. Effect of frosts upon forest vegetation. Forest Quarterly 

2:14-21. 1903. 
Stone, G. E. Winter-killing. Massachusetts Agr. Exp. Sta. Ann. 

Kept. 18:228-233. 1906. 
Stone, G. E. Frost cracks, winterkilling of cork cambium and sun 

scald. In Shade trees, characteristics, adaptation, diseases and 

care. Massachusetts Agr. Exp. Sta. Bui. 170:204-208, figs. 

77-80. 1916. 



50 



MANUAL OF TREE DISEASES 



Fig. 1. — Frost- 
cracks in a maple, 
which have opened 
for several succes- 
sive winters. 



Frost-Cracks 
Caused by low temperatures 

There are two sorts of 
frost-cracks which are 
common types of injury 
to trees caused by low 
temperatures. Some 
frost-cracks may ruptiu'e 
the bark and result in 
open splits in the trunk 
(Fig. 1). The callusing 
at the edges of this split 
and the repeated opening 
and healing usually result 
in a ridge of tissue which 
increases in prominence 
year after year (Fig. 2). 
At other times, frost- 
cracks which do not rup- 
ture the bark may occur 
in the wood. These 
either do not show ex- 
ternally or appear as 
slight frost-ridges. They 
are important when the 
trunk is to be utilized as 
lumber, since the defects 
cause the product to be 
of inferior quality. The 
splitting open of trunks 
is more common with 
some trees than others. 
Deciduous trees with 



Fig. 2. — The same 
tree shown in Fig. 1, 
as it appears during 
the summer. 



BODY AND BRANCH DISEASES AND INJURIES 51 

wide medullary raj^s, such as oak, beech, ash and maple, are 
more susceptible to cracking than conifers, although spruce 
and fir crack frequently. Larger trees, especially those which 
are isolated and growing on heavy wet soils, are more often 
affected. 

As the temperature falls below the freezing point, more 
and more water is withdrawn from the cells of the wood 
and frozen into ice crystals. This results in the contraction 
of the wood, the same as if the water were withdrawn by 
evaporation. The result is a shrinkage tension which, 
because of the difference in degree of contraction between 
medullary-ray tissue and lignified wood}' tissue, exerts a greater 
pull in the direction of the circumference than in the radial 
direction. The tension thus developed is considerable before 
the bark finally gives way and the trunk splits open. The 
rupture is usually accompanied, because of its suddenness, 
by a loud report. The splitting is entirely comparable to the 
checking of timber on drying, except that the water is not 
lost in evaporation, but remains around and within the elements 
of the wood as ice crystals. With the return of warmer weather, 
the tissues reabsorb the water lost in freezing and the crack 
closes. Wound-tissue is formed, but the weakness at this 
point usually results in a reopening of the crack each winter. 

References 

Chandler, W. H. The killing of plant tissue by low temperature. 
Missouri Agr. Exp. Sta. Research Bui. 8 : 141-309. 1913. 

Zon, R. G. Effects of frost upon forest vegetation. Forest Quarterly 
2:14-21. 1903. 

Stone, G. E. Frost cracks. In Shade trees, characteristics, adapta- 
tion, disease^s and care. Massachusetts Agr. Exp. Sta. Bui. 
170 : 204-205, figs. 77-78. 1916. 

Hartig, R. Injuries due to atmospheric influences and fire. The action 
of frost. Iti Text-book of the diseases of trees, pp. 282-294, figs. 
157-158. 1894. 



52 MANUAL OF TREE DISEASES 

Sun-Scald 

Caused by high temperatures and low humidity 

The actual scorching of the bark of certain susceptible trees 
occurs under circumstances in which previously shaded smooth- 
barked limbs are suddenly exposed to the full insolation of the 
afternoon sun. Severe pruning or the removal of neighboring 
trees make possible such injury. Beech, spruce and pines are 
subject to sun-scald. This type of injury is due to the direct 
wilting and drying-out of the bark-tissues caused by excessive 
heat and the action of the wind. Small twigs may be killed 
in the same way, especially at times when the leaves sun- 
scorch (see page 22). Although this is the type of injury 
to which the term sun-scald should be restricted, it is more 
probable that the low humidity of the air and the drying action 
of the wind are more closely connected with the injury than the 
actual degree of temperature reached by the sun's action. 

References 

Hartig, R. Bark scorching, sun-cracks and deficiency of light. In 
Text-book of the diseases of trees, pp. 294-299, fig. 159. 1894. 

Stone, G. E. Sun scald. In Shade trees, characteristics, adapta- 
tion, diseases and care. Massachusetts Agr. Exp. Sta. Bui. 170 : 
207-208. 1916. 

Lichen-Injury 

Caused by species of lichens 

No definite work has been undertaken to determine the amount 
of damage caused by lichens. Opinions of writers vary, but 
many think that trees are injured by the severe infesta- 
tions that sometimes occur, especially in places where the air 
is continuously humid. Under such atmospheric conditions 
and where the nature of the soil causes slow growth, the bark 
of trees may be covered with lichens of different kinds. It is 
thought that more rapidly growing trees, in good soil, form their 



BODY AND BRANCH DISEASES AND INJURIES 53 

bark so rapidly that it scales off and does not give the lichens 
time to become established in abundance. Both the foliaceous 
and crustaceous forms of lichens are found growing on bark, 
often to the extent that they entirely cover the trunk and 
limbs. The common supposition is that they are responsible 
for the poor condition of the trees on which they occur, but for 
the reason just stated it seems more likely that the tree is 
covered with lichens because it is slow-growing. 

It is supposed, since the lichens do not penetrate the bark 
and establish any true parasitic relation with the tree, that 
any damage they cause is due to their mechanical interference 
with the respiration and transpiration processes which go on 
through the lenticels in the bark. The effects of shading and 
continuously holding moisture may be considered to increase 
the damage caused by lichens ; consequently the crustaceous 
forms seem to be more injurious because they grow more tightly 
appressed to the bark. 

The eradication of lichens can be easily accomplished by 
spraying the affected parts in the ordinary way with bordeaux 
mixture. The lichens will die within a few days. The best 
results are obtained if the spraying is done when the leaves 
are oft' the tree, since all parts of the infested trunk and limbs 
can be more surely and easily reached with the mixture. For 
directions for making bordeaux mixture, see page 358. 

References 

Waite, M. B. Experiments with fungicides in the removal of lichens 
from pear trees. Jour. Mycology 7 : 264-268, pis. 30-31. 1893. 

Hartig, R. Pseudo-parasites, hi Text-book of the diseases of trees, 
pp. 35-36. 1894. 

Slime-Flux 

Caused by the fermentation of oozing sap 

Wounds of various kinds, in such trees as birch, elm and maple 
which bleed very profusely, may develop a chronic exudation 



54 MANUAL OF TREE DISEASES 

of slimy mal-odorous ooze. Certain species of fungi closely 
related to the yeasts are commonly found in this ooze, along 
with other fungi and bacteria. Fermentation of the sap which 
is exuded from the fresh wound causes the death of the bark 
and wood adjacent to the wounded tissue and often large areas 
of bark are killed. It is not known what specific action the 
different organisms in the slime exercise in causing the death 
of the bark. It is supposed that they do not act as parasites 
but rather that the products of fermentation slowly produce the 
death of the adjoining tissues. 

The most important step in preventing slime-flux is to care 
for any wounds before the ooze begins to form. Trees which 
bleed commonly should be watched so that any wounds that 
occur can be shaped and immediately prepared for rapid 
healing. If bleeding continues and a wound-dressing will not 
adhere, the surface of the wound may be cauterized with a 
gasoline torch. Old wounds which have developed slime- 
flux should be cleaned and treated in the same way. For 
directions regarding tree surgery methods, see page 345. 

Mistletoe Diseases 

Caused by species of Razoumof skya (Areeuthobium) and Phoradendron 

Several species of parasitic flowering plants, belonging to 
the family Loranthacese, cause considerable damage to trees. 
The composite species Phoradendron fiavescens, the American 
mistletoe, grows on many kinds of deciduous trees and shrubs 
in southern United States, while numerous species of the genus 
Razoumofskya (the dwarf mistletoes) grow on conifers, causing 
much damage in the forest, especially west of the Rocky Moun- 
tains.^ In Europe members of the mistletoe family are impor- 
tant tree parasites. 

* The generic name Areeuthobium is retained as one of the nomina conservanda 
of the International Rules for Botanical Nomenclature. Under the American 
Code, the name Razoumofskya is revived. 



BODY AND BRANCH DISEASES AND INJURIES 55 

Spruce, pine, larch, fir and hemlock are attacked by more 
or less restricted species of Razoumofskya. These parasitic 
plants are very small and not easily recognized among the 
green needles of the host. When the mistletoe seed germinates, 
root-like sinkers are pushed down into the wood of the branch. 
The young mistletoe plant then obtains its water and food 
materials by robbing the host. The damage done by the 
dwarf mistletoes is largely due to the stimulus reactions set 
up. Excessive growth occurs in the part of the tree attacked, 
and large numbers of short bushy branches are produced which 
form what are commonly known as witches'-brooms. These 
brooms are often very large, and the excessive growth results 
in lessened vigor of the portion of the limb beyond the broom. 
When several brooms grow on a tree, its lumber value de- 
preciates because of the diminished annual growth. Another 
damaging effect is due to the weight of the brooms when 
covered with ice and snow, causing them to break off, leaving 
wounds which are easily infected by various wood-rot fungi. 

Following is a list of the dwarf mistletoes (species of Ra- 
zoumofskya) which grow parasitically on conifers in the western 
United States : -7- 

On fir (Abies) 

R. Douglasii abictina (Engelm.) Piper. Rocky Mountains and west- 
ern United States 

R. occidentalis abictina (Engelm.) Co\alle. Pacific Coast and Utah 
On fir (Pseudotsuga) 

R. Douglasii (Engelm.) Kuntze. Rocky Mountains and Pacific 
Coast 
On hemlock 

R. tsugensis Rosend. Northwestern United States 
On larch 

R. laricis Piper. Northwestern United States 
On pine (five needle soft pines) 

R. cyanocarpa (A. Nelson) Rydberg. Western United States 

R. Blumcri (A. Nelson) Standley. Ai'izona 
On pine (pinon, nut pines) 

R. divaricata (Engelm.) Coville. Central and southern Rocky 
Mountains and California 



# 



56 



MANUAL OF TREE DISEASES 



On pine (three and two to three needle, pitch pines) 
R. campylopoda (Engelm.) Piper. Pacific Coast 
R. cryptopoda (Engelm.) Coville. Central and southern Rocky 

Mountains 
Ji. americana (Nutt.) Kuntze. Rocky Mountains to Sierra Nevada 

Mountains 




Fig. 3. — Mistletoe (Phoradendron pauciflorum) growing on white fir. 



The only representative of the dwarf mistletoes occurring 
in eastern United States is R. pnsiJIa, which causes witches'- 
brooms on spruce. A discussion of this disease will be found 
on page 321, 



BODY AND BRANCH DISEASES AND INJURIES 57 

Several species of the genus Phoradendron attack the junipers 
in southwestern and western United States. These mistletoes 
are sometimes found also on fir, cypress and incense cedar. They 
are much larger plants than the dwarf mistletoes and make a 
part of their own food materials, since they have green leaves. 
The main damaging effects of these mistletoes are the starving 
of the portion of the limb from the point of attack outward 
and the production of brittle swellings which allow the limbs 
to be easily broken off by wind or excessive weight (Fig. 3). 

Practically all kinds of deciduous forest- and fruit-trees are 
attacked by the mistletoe, Phoradendron flavescens, in southern 
United States. This mistletoe is a large form and has green 
leaves. The berries are sticky and are distributed by birds. 
The roots from the germinating seed penetrate the wood and 
establish the parasite. The chief damaging effects arise from 
the starving of the branch beyond the point of attack and the 
shading of the foliage of the host. The branch at the point 
of attack becomes , larger and greatly deformed. Sometimes 
on certain hosts, abnormal branching occurs and witches'- 
brooms are formed. 

Following is a list of the parasitic leafy mistletoes (species 
of Phorodendron) of the United States arranged under the 
kind of trees they attack : — 

Alder 

P. Engelmanni Trelease. Texas 

P. macrophyllum Cockerell. Arizona 

P. longispicum Trelease. California and Arizona 
Apple 

P. macrophyllum Cockerell. Arizona 

P. flavescens Nuttall. Central and southeastern states 
Ash 

P. macrolomum Trelease. Florida 

P. Eatoni Trelease. Florida 

P. macrophyllum Cockerell. Arizona 

P. Cockerellii Trelease. New Mexico and Texas 

P. longispicum Trelease. California and Arizona 

P. flavescens Nuttall. Central and southeastern states 



58 MANUAL OF TREE DISEASES 

Basswood 

P. Jlavescens Nuttall. Central and southeastern states 
Beech 

P. Jlavescens Nuttall. Central and southeastern states 
Birch 

P. Jlavescens Nuttall. Central and southeastern states 
Buckeye 

P. Jlavescens Nuttall. Central and southeastern states 

P. villosum Nuttall. Pacific Coast 

P. longispicii7n Trelease. California and Arizona 
Cedar 

P. Libocedri Howell. California, Oregon and Nevada 
Cherry 

P. Jlavescens Nuttall. Central and southeastern states 

P. macrotomum Trelease. Florida 

P. macrophyllum Cockerell. Arizona 
Chestnut 

P. Jlavescens Nuttall. Central and southeastern states 
Cypress 

P. paucijlorum Torrey. California and Arizona 
Elm 

P. Jlavescens Nuttall. Central and southeastern states 
Fir 

P. paucifloi-um Torrey. California and Arizona 
Gum (Nyssa) 

P. Jlavescens Nuttall. Central and southeastern states 

P. macrotomum Trelease. Florida 
Hackberry 

P. Jlavescens Nuttajl. Central and southeastern states 

P. Engelmanni Trelease. Texas. 

P. macrophyllum Cockerell. Arizona 
Hickory 

P. Jlavescens Nuttall. Central and southeastern states 
Honey locust 

P. Jlavescens Nuttall. Central and southeastern states 
Juniper. 

P. juniperinum Engelmann. Colorado, Utah and New Mexico 

P. ligatum Trelease. Nevada and Pacific Coast 

P. capitellatum Torrey. New Mexico and Arizona 

P. Bolleanum Eichler. Texas 

P. densum Torrey. Pacific Coast 
Locust 

P. Jlavescens Nuttall. Central and southeastern states 

P. macrophyllum Cockerell. Arizona 

P. villosum Nuttall. Pacific Coast 

P. loiigispicum Trelease. Pacific Coast 



BODY AND BRANCH DISEASES AND INJURIES 59 

Maple 

P. Jlavescens Nuttall. Central and southeastern states 
Oak 

P. Jlavescens Nuttall. Central and southeastern states 

P. Jlavescens orbiculalum Engelmann. South central states 

P. macrotomum. Trelease. Florida 

P. Engelmanni Trelease. Texas 

P. villosum Nuttall. Pacific Coast 

P. Coryce Trelease. Arizona and New Mexico 

P. Harvardianujn Trelease. Texas 

P. lojigispicum Trelease. California and Arizona 
Plum 

P. Jlavescens Nuttall. Central and southeastern states 

P. macrotomum Trelease. Florida 

P. 7nacrophyllum Cockerell. Arizona 
Poplar 

P. Jlavescens Nuttall. Central and southeastern states 

P. macrophyllum Cockerell. Arizona 

P. Cockerellii Trelease. New Mexico and Texas 

P. villosum Nuttall. Pacific Coast 

P. longispicum Trelease. California and Arizona 
Red Gum 

P. Jlavescens Nuttall. Central and southeastern states 
Sycamore 

P. Jlavescens Nuttall. Central and southeastern states 

P. macrophyllum Cockerell. Arizona 

P. lo7igispicum Trelease. California and Arizona 
Walnut 

P. Jlavescens Nuttall. Central and southeastern states 

P. macrophyllum Cockerell. Arizona 

P. longispicum Trelease. California and Arizona 
Willow 

P. Jlavescens Nuttall. Central and southeastern states 

P. macrophyllum Cockerell. Arizona 

P. Cockerellii Trelease. New Mexico and Texas 

P. villosum Nuttall. Pacific Coast 

P. longispicum Trelease. California and Arizona 

Control. 

As a means of control of these parasites on shade and orna- 
mental trees, the mistletoe plants should be cut off as close to 
the tree as possible. New sprouts may be sent out and a 
second or third cutting then becomes necessary. Also the 



60 MANUAL OF TREE DISEASES 

tips of the affected branches may be pruned off, thus removing 
permanently the infected parts of the tree. However, if the 
tree is badly infested and new plants persist in appearing, 
this procedure results in excessive pruning and a deformed 
tree. It is said that the parasites may be successfully eliminated 
by the first method and the tree left to its natural form of 
growth if proper and constant attention is given to the work. 

In the forest where these pests often occur on twenty-five to 
fifty per cent of the stand of conifers, it is essential that forest 
management plans should incorporate the elimination of all 
affected trees during lumbering operations. Seed trees which 
are left should be chosen with regard to their freedom from 
mistletoe. 

References 

Bray, W. L. The mistletoe pest in the southwest. U. S. Dept. Agr. 

Bur. PI. Ind. Bui. 166 : 1-39, pis. 1 and 2, figs. 1-7. 1910. 
Weir, J. R. Mistletoe injiu-y to conifers in the northwest. U. S. 

Dept. Agr. Bui. 360 : 1-39, pis. 1-4, figs. 1-27. 1916. 
Weir, J. R. Larch mistletoe : some economic considerations of its 

injurious effects. U. S. Dept. Agr. Bui. 317 : 1-25, figs. 1-13. 

1916. 
Hedgcoek, G. G. Notes on some diseases of trees in our national 

forests. V. Phytopathology 5 : 175-181. 1915. 
Hartig, R. Phanerogams. In Text-book of the diseases of trees, 

pp. 23-34, figs. 1-7. 1894. 
Trelease, W. The genus Phoradendron, pp. 1-224, pis. 1-245. Univ. 
of 111. 1916. 

Electrical Injuries 

Caused by current electricity and lightning 

Trees may be more or less seriously injured by contact with 
service wires carrying current electricity and by strokes of 
lightning. In both types of injury the actual killing of the 
living tissues of the tree is due to the production of heat when 
the current meets with the high resistance of the tissues. INIuch 
of the damage often ascribed to overhead wires is not so much 



BODY AND BRANCH DISEASES AND INJURIES 61 

due to electrical injury as to the severe and unscientific pruning 
along pole-lines. 

Two types of injury due to current electricity are recognized. 
Alternating and direct currents of low voltage, carried in in- 
sulated wires, cause but little damage, except when local burn- 
ing occurs at places where the insulation is rubbed away by 
contact w^ith the tree. The resistance of the bark and wood 
is so great that the amount of the low voltage current which 
passes down the tree and into the ground is not sufficient to 
raise the temperature sufficiently to kill living cells. The 
damage is due rather to the combination of mechanical and 
burning injury at the point of contact, resulting in rough open 
wounds which become weak points in the limb and centers of 
infection for wood-rot fungi. 

Direct current electricity causes more damage than does the 
alternating current. High voltage, uninsulated feed and 
trolley wires carrying direct current, when the charge is posi- 
tive, cause local burning but do not kill the tree. The short 
circuiting is more complete in wet weather, when the tree is 
covered with a film of water. In cases in which the rails of 
electric railroads carry the positive charge, and the trolley and 
feed wires the negative, the effect of contact of the wires with 
a tree is more serious and often results in death. The dif- 
ference in effect is due to the root surface being imbedded in 
the soil-water which is a good conductor and the high voltage 
positive current is transmitted to the roots of the tree which 
expose a large surface. For this reason, more current enters 
the tree than in the case in which the wires carry the positive 
charge, and severe burning of the living tissues occurs in the 
roots and at the base of the trunk, often killing the tree. 

Lightning acts in the same way as current electricity, except 
that a large variety of other effects may also occur. The usual 
type of lightning-injury is a groove plowed in the bark and wood 
down the trunk. This groove is straight when the wood- 



62 MANUAL OF TREE DISEASES 

fibers are straight and may run round tlie tree when the grain 
is spiral. At times, various other types of injury may occur, 
such as : stripping of all the bark from the tree, shattering of 
the top of the tree, splitting and otherwise shattering the 
entire tree, and shattering the base and allowing the tree other- 
wise uninjured to fall over. All of these types of violent in- 
jury are caused by lightning in a way that is not understood. 
It is known that lightning discharges are of high voltage. 
When the damage is greatest at the base of the tree, the posi- 
tive charge was probably carried by the earth, and when the 
top is shattered, the positive charge was in a stratum of air or 
a cloud above the tpee. Many divergent opinions concerning 
the susceptibility or immunity of different species of trees to 
lightning stroke have been stated. Recent investigations in 
this country and in Europe have shown that trees of all kinds 
are liable to lightning stroke and that those which are isolated, 
on high ground, or are more deeply rooted than surrounding 
trees are the most liable to be struck. The idea that trees of 
a certain species are more often struck than others is usually 
due to the fact that they are more abundant or more dominant 
than other species. 

Another less common type of lightning-injury is when groups 
of trees die within a few days after the stroke and others around 
these die during the next few years. This type of injury is 
explained by the fact that the positive charge was in the earth 
and when the flash occurred the tissues of the roots and the 
bark at the base of the tree were killed. A few of the trees 
were injured to the extent that they died quickly, for want of 
water and raw food materials from the soil ; others around 
which did not receive such a heavy shock were only injured 
in such a way that they were prevented from sending prepared 
food to the roots and died later. This type of injury then is 
similar to the effects produced by girdling. 

The matter of protecting shade-trees from damage by elec- 



BODY AND BRANCH DISEASES AND INJURIES 63 

trie currents earried by wires is of importance in every city. 
Any device made of a substance which is a non-conductor 
(porcelain, or rubber) and which keeps the wires from coming 
into contact with the Hmbs, will prevent short circuiting. If 
the additional injury caused by rubbing is to be avoided, some 
arrangement must be made for locating the wires so that they 
are taut and do not come within three or four inches of the limbs. 



References 

Stone, G; E. Electrical injuries to trees. Massachusetts Agr. Exp. 
Sta. Bui. 156 : 1-19, pis. 1-5. 1914. 

Plummer, Fred G. Lightning in relation to forest fires. U. S. Dept. 
Agr. Forest Ser. Bui. Ill : 1-39, pis. 1-2, figs. 1-16. 1912. 

MacDougal, D. T. Effect of lightning on trees. Proc. N. Y. Bot. 
Gard. 3 : 1902. 

Hartig, R. The effects of lightning. In Text- 
book of the diseases of trees, pp. 302-304. 
1894. 

Galls 



Caused by various insects, fungi and bacteria 

Trees of all kinds often develop large or 
small galls of various types on the trunk 
and limbs. The causal agents in many cases 
have not been studied, but it is supposed 
that certain insects, fungi and bacteria are 
frequently responsible for the irritation 
which results in the overgrowth in the 
tissue. Mechanical injuries may in some 
cases also cause galls. The causal agent 
initiates abnormal division of the cells and 
the tissues may continue the over-develop- 
ment for years after the cause is gone. 
The limb-galls of poplar are known to be 
caused in some cases by the crown-gall 




Fig. 4.- 
branch 



64 MANUAL OF TREE DISEASES 

bacterium (see page 304). The galls commonly found on oak 
are probably initiated by insects (Fig. 4). Galls are usually 
formed of abnormal wood and bark. They may frequently 
serve as a place of entrance for wood-rotting fungi when the 
bark is injured. 

Wood-Rots 

Caused by fungi of the order Hymeniales 

The wood in the roots, trunk and branches of trees is a 
very stable and durable substance. While still a part of 
the living tree, the heartwood is of but little value to the tree 
except f , r support and is essentially dead tissue. During 
the life ( f the tree and after it is made into timber and its 
various derivative products, wood remains durable and intact 
except when fire, insects and wood-decaying fungi destroy it. 
Were it not for these three destructive factors, the wood in the 
living tree would remain sound until utilized and would then 
be useful for an indefinite time, until ordinary weathering and 
abrasion made it worthless. By eliminating the factor of decay 
in all forms of timber now in use, the saving in the annual cut 
for replacement would amount, for the United States as a 
whole, to nearly a hundred million dollars. Stated in another 
way we would need to produce less than half the timber now 
used if the factor of decay were eliminated. In the forest, 
under the present systems of management in this country, the 
losses from wood-rots reduce enormously the yield of timber. 
Likewise, with trees outside the forest, wood-rots are more 
or less destructive, and are the factor which largely determines 
the length of life of the tree. In the forest and outside, many 
of the fungi which cause decay of the heartwood also extend 
their activities into the sapwood and bark. When the latter 
tissues are attacked, certain parts of the trees die because of 
the interference with the necessary transportation of food 
materials, between the roots and leaves. 



BODY AND BRANCH DISEASES AND INJURIES 65 

The fungi which destroy wood are mostly of one general type 
and are commonly known as the bracket-fungi or polypores. 
Some of the toadstools also are wood-destroyers. Several 
species of these two types of fungi are known which enter the 
wood of living trees and cause its decay. A few of these are 
active parasites, which advance into and kill living tissue in 
the sapwood and bark. The others attack only the heart- 
wood. Numerous other ch;sely related bracket-fungi and toad- 
stools never enter the wood of living trees but exist as sapro- 
phytes, destroying wood after the tree is dead either in the 
forest or while it is in use as a timber product. Some of these 
latter forms often appear to be parasitic, when they are found 
growing on a living tree which is severely injured. The para- 
sitism is only apparent, however, since the wood is exposed 
to weathering and is essentially in the same condition as if 
the tree were dead. The various important wood-rots are 
described under the kind of tree commonly affected, but since 
the life history of all of the causal fungi is essentially the same, 
a general discussion of the mode of infection, nature of the 
process of wood-decay, production of fruiting-bodies, dissemina- 
tion of the spores and methods of control is given here to 
avoid repetition or lack of detail concerning these points under 
the individual discussions. 

Mode of infection. 

Normally the tree is protected from Invasion of wood-de- 
stroying fungi by the bark. But whenever the bark is injured 
to the extent that the sapwood or heartwood is exposed for 
any considerable length of time, infection may occur by the 
lodgment and germination of the spores on the exposed wood. 
Conifers and some deciduous trees are capable of producing 
resinous and gummy substances, where the sapwood and 
bark are wounded. These substances when exuded in quantity 
cover the wounded area and protect it from infection. For 



66 MANUAL OF TREE DISEASES 

this reason such trees are usually free from wood-rots until 
heartwood is formed. The larger part of the deciduous trees 
form no such protective wound exudations, and injuries which 
cause the exposure of the sapwood often result in infection by 
some sapwood-rotting fungus. Wounds of all sorts may be 
caused in the forest by browsing animals, woodpeckers, boring 
insects, wind, snow and ice breakage of limbs, fire scars at the 
base, and natural pruning of limbs, while out of the forest many 
additional agencies may cause wounds. Some wood-destroy- 
ing fungi attack commonly the wood of the roots. Wounds 
in the roots afford places of infection, and from the roots the 
mycelium may spread upward into the lower part of the trunk. 
But the most common mode of entrance for fungi is by way of 
the wood exposed when branches are broken or pruned-off, either 
naturally or artificially. The proper method of cutting the 
limb so as to leave no projecting stub cannot be too greatly 
emphasized in the case of shade and ornamental trees (see page 
346). The wound must be flush with the parent limb in order 
that the callus may cover it. In the meantime, while the 
callusing is taking place, the exposed wood should be covered 
with a wound-dressing (see page 348). Total disregard for 
these two procedures in pruning leaves the way open for most 
of the damage to valuable trees by wood-rotting fungi. In 
the forest a certain amount of wounding may be avoided, but 
the main method of control is by the removal of the sources 
of infection. 

The spores of a fungus causing wood-rot of a certain kind of 
tree, after lodging upon exposed sapwood or heartwood of that 
tree, will germinate in the presence of moisture and de\'elop 
a mycelium which grows into the wood. The sapwood-rotting 
fungi immediately spread their mycelium in all directions and 
soon large dead areas result. The species which attack the 
heartwood preferably, develop mycelium which reaches down 
through the wood of the branch stub into the heartwood of the 



BODY AND BRANCH DISEASES AND INJURIES 67 

trunk. It then extends its growth upward, downward and 
radially, until it may spread out through the sapwood and bark. 

Nature of the process of wood-decay. 

The heartwood of trees consists of a complex arrangement 
of empty and lifeless cell-walls. Previously, while this tissue 
was still sapwood and when a portion of the cells were alive, 
it carried on the function of transporting water and food 
materials between the roots and leaves. During the process 
of the development of the sapwood, the cell-walls were ligni- 
fied. To this modification of the cell-walls is due all the 
properties of strength, color and durability which make woody 
tissue different from the tissues of the non-woody or herbaceous 
plants. In the lignified condition, wood is immune to the 
ordinary agencies which so easily destroy non-lignified tissue. 
The wood-rotting fungi, however, excrete certain enzymes 
which abstract the lignin from cell-walls ; also in most cases 
they are able to dissolve completely the basic structure of the 
cell-wall by other enzymes. These two types of enzymes 
effect the partial or complete solution of the cell-walls. In 
either case, the wood is no longer of value as wood, since the 
abstraction of the lignin destroys the properties of strength 
and leaves a soft and spongy substance. In the entrance of 
the mycelium into sound wood, preliminary changes take 
place which liberate resins and gums and these may pass out 
into the sapwood and bark. Sometimes the accumulation of 
these substances retards or arrests the further spread of the 
mycelium. Color changes usually accompany the decay, 
whereby the rotted wood is left almost white or is colored 
brown or yellovv^. These colors are due to decomposition 
products which stain the wood. When the action is general, 
a uniformly rotted area results, but, in many wood-rots, localized 
nest's of the mycelium cause the complete solution of small 
areas of the wood. This leaves pockets or holes separated by 



68 



MANUAL OF TREE DISEASES 



only partially decayed wood. Another common distinguish- 
ing mark which may accompany wood-decay is the production 
of black lines or discolored zones which usually mark the place 
where the most active changes are occurring in the deligni- 
fication process. The colored zones are due to dark colored 

oxidation products which 
stain the mycelium and 
cell-walls of the wood. 

The mycelium of wood- 
rotting fungi uses the 
dissolved wood-tissue as 
food material. After a 
considerable amount of 
this food is obtained and 
stored, the production of 
the fruiting-bodies be- 
gins. For this purpose 
a tissue-like development 
of closely tangled my- 
celium, in the shape of 
a knob, usually forms at 
the original point of in- 

FiG. 5. — UnJer surface of a polypore, show- fectiou. The food ma- 
ingopcn ends of spore-bearing tubes. En- terials from all directions 
larged (several tnucs). 

are transported to this 
point and the fruiting-body develops an upper sterile surface and 
a fertile suspended layer of spore-bearing tissue on the under 
surface. In the case of the toadstools the spores are borne on 
the sides of pendent plates or gills (Fig. 8, page 81), and in 
the bracket-fungi or polypores, they are borne on the inner sur- 
face of perpendicular tubes which are open at the lower end 
and are visible to the naked eye as small holes in the lower 
surface of the fruiting-body (Fig. 5). Besides the character- 
istic action of the mycelium of the different species of fungi 




BODY AND BRANCH DISEASES AND INJURIES 69 

causing the wood-rots, the characters of the friiiting-bodies 
serve to identify the causal fungus, if they are definitely as- 
sociated with the rot. The correct determination of the dif- 
ferent species of bracket-fungi is, however, not easy in some 
cases. The number of species of annual forms represented in 
the United States is greater than that of the perennial forms. 
A generic distinction between the annual and perennial forms 
is recognized and they have been named respectively Po- 
lyporus (po-lip -pore-us) and Fomes (fo-meez). Other genera 
have been split off from these two, which probably represent 
a more natural classification. Since, however, the simpler 
and more artificial classification is still used by laymen and 
most scientists, the genera Polyporus and Fomes are used in 
the discussion of the wood-rot fungi in this book. For a 
synonymy of polypore names, see the appendix, page 364. 
The species of Polyporus usually produce a more or less fleshy 
or corky fruiting-body which is soon destroyed by insects or 
decay and rarely functions in producing spores for more than 
the single season. The species of Fomes, on the other hand, 
form hard, woody structures which develop a new layer of 
tubes on the under surface each year as long as food material 
is being obtained by the mycelium, in its advance into normal 
wood. In this manner the size of the fruiting-body increases 
yearly and its age may be determined by counting the layers 
of tubes when the fruiting-body is split perpendicularly. 

Dissemination of the spores. 

The spores of the bracket-fungi are borne in groups of four, 
each on a tiny spine, at the ends of branches of the mycelium 
which project from the inner sides of the tubes. ' When mature, 
these spores are shot from their attachment with just enough 
force to bring them to the center of the tube, and then they 
drop, out of the open end at the bottom. The wind, or even the 
slightest breeze, serves to carry the spores for long distances, 



70 MANUAL OF TREE DISEASES 

since they are very light and buoyant. MilUons of spores are 
disseminated from a single fruiting-body during a few days 
after they become mature. They are somewhat sticky and 
adhere to any object with which they come in contact. The 
larger part of them never reach suitable places where infection 
may be accomplished. However, a sufficiently large number 
is produced that a few usually find lodgment where infection 
is possible. Wounds such as the splintered ends of the branch- 
stubs which hold moisture readily are most likely to become 
infected. The spores are very short-lived and suitable con- 
ditions of moisture must be encountered in order to have ger- 
mination take place. The germ-tube of the spore produces short 
branches of mycelium which immediately begin the decay of 
the wood at the point of infection, and as soon as a firm foot- 
hold is gained, a copious growth of the mycelium occurs, which 
spreads rapidly. 

Control of wood-rots. 

Wood-rot diseases are more abundant and destructive in 
the forest than in individual trees grown for shade or ornament. 
Conditions in the forest are ideal for the development of these 
fungi. AH sorts of wounds are available for infection and thus 
dissemination and germination of the spores is more efficient 
in causing a higher percentage of infection. Another factor 
which makes wood-rots more serious in the forest is that great 
quantities of fallen trunks and branches are present on which 
fruiting-bodies of most of the wood-rot fungi continue to be 
produced in great abundance. Outside the forest, the absence 
of these conditions makes infection less common. A few of 
the wood-rots, however, are important diseases of shade-trees. 

In controlling these rots, tree surgery methods are effective 
if the wood-rot is not too far advanced and if the expense is 
considered justified by the value of the tree. The methods 
for eliminating heartwood- and sapwood-rots are discussed under 



BODY AND BRANCH DISEASES AND INJURIES 71 

tree surgery, page 345. The necessary care in pruning to leave 
a wound which will heal most rapidly and protecting the wound 
in the meantime by the use of wound-dressings are important 
measures for reducing wood-rots to a minimum. These opera- 
tions are also more fully discussed under tree surgery methods. 
The immediate destruction of newly developing fruiting-bodies 
of all kinds in the vicinity of trees to be protected will reduce 
greatly the amount of infection. 

In the forest, the factors concerned in the complex of soil, 
atmospheric and biologic relations, influence greatly the yield 
and quality of timber that is realized. JNIethods of forest 
management in this country have seldom taken into consid- 
eration many of these vital factors, one of the most important 
of which is the control of the wood-rotting fungi of living trees. 
The subject of forest pathology is too complex to be adequately 
dealt with in a small space and is outside the field of this book. 
A simple method of disease control in the forest is the elimina- 
tion of all diseased trees at the time cutting operations are 
in progress. For some types of forests and systems of selec- 
tion for cutting, this procedure is not economically possible. 
Thus it will be possible to control the loss factor due to decay 
only when all the complex relations existing in the forest have 
been studied for different types and localities. Before control 
measures can be incorporated into scientific forest regulation, 
such points as the following must be determined : the relations 
which determine the rate of growth and general health of the 
trees, the extent, nature and cause of wounds, the life history 
of the wood-rotting fungi, the relative susceptibility of different 
species and different age classes, and many other relative factors. 

References 

Schrenk, Hermann von. Fungous diseases of forest trees. U. S. Dept. 

Agr. Yearbook 1900: 199-210, pis. 21-25. 1901. 
Meinecke, E. P. Forest pathology in forest regulation. U. S. Dept. 

Agr. Bui. 275 : 1-62. 1916. 



CHAPTER IV 
ROOT DISEASES AND INJURIES 

The roots serve both for anchorage and for gathering from 
the soil the water and dissolved raw materials needed by the 
tree in its growth. The structure of certain types of soil, 
and the food materials contained, often determine the kinds 
of trees which will grow best in it. However, it is not the 
intention to discuss here the adaptability of different species to 
soil-types or of the poor growth or injuries resulting from a 
lack of such adaptability. Although a tree may be growing in 
suitable soil and obtaining from it the proper materials for 
normal growth, there are other factors which often inter- 
vene to cause injuries to the root system. Any such injuries 
to the roots of the tree may impair certain functions or destroy 
living tissues and cause various symptoms of disease to appear 
in the aerial portions of the tree. 

In diagnosing tree troubles, the possibility of root diseases 
should be considered and care should be taken to ascertain 
whether or not the condition of the roots may be the primary 
cause of the difficulty. Impairment of the root functions may 
be due t"o such conditions as : too much water in the soil, causing 
drowning ; too little water because of sod, pavements, or packed 
soil above the roots ; poisonous gases or over-abundance of 
certain food materials applied to the roots with fertilizers ; and 
the attacks of certain parasitic fungi and bacteria which invade 
and kill living tissue. These various injurious factors work 
more or less slowly, and the usual symptoms noticed in the parts 
above ground are : slow growth, thin foliage, sun-scorch of the 

72 



ROOT DISEASES AND INJURIES 73 

leaves, early fall of leaves in autumn, death of certain entire 
branches, stag-head, and lichens on the bark. When such 
general symptoms of decline occur without apparent associa- 
tion with a cause in the branches, leaves or atmospheric con- 
ditions, the presence of a root trouble may be suspected. 

Drying and Drowning 
Caused by too little and too much water in the soil 

Trees must obtain at all times enormous quantities of water 
from the soil, during the period when the leaves are expanded. 
With a normal water supply and a healthy root system, a tree 
is naturally so balanced in its development of roots and leaf- 
surface, that it is able to supply the water lost in transpiration 
from the leaves, except under the most abnormal atmospheric 
conditions. But if the supply of water is limited because the 
natural rainfall does not soak into the soil, the leaves may tran- 
spire more water than the roots can take up in a given length of 
time. This condition will cause sun-scorch of the leaves and 
if repeated year after year may cause the death of the tree (see 
page 22). 

The other extreme of too much water in the soil may result 
in more speedy death of the tree. The tips of the roots, which 
are in contact with the soil-particles and absorb water and food 
materials, must at the same time obtain a ready supply of air 
to make healthy growth and perform their function of absorp- 
tion. The older parts of the roots must also have access to a 
supply of air in order that the living tissues they contain may 
function in growth and transporting food materials and water 
to the parts above ground. If the amount of water in the soil 
is excessive, it drives out the air, thus disturbing the balance of 
air and water necessary to plant growth. This results in slow 
or rapid death of the roots by drowning. The leaves may show 
sun-scorch injury the same as when too little water is present. 



74 MANUAL OF TREE DISEASES 

This may seem peculiar, since there is an over-abundance of 
water in the soil, but it is explained by the fact that the trans- 
porting of the water to the trunk is dependent on the healthy 
condition of the roots and when these are injured, the power 
to absorb water is diminished accordingly. Therefore, al- 
though there is plenty of water in the soil, it cannot be supplied 
to the leaves. 

The remedy for such conditions of abnormal . water supply 
may be undertaken after the symptoms are noted, if the re- 
covery of the tree seems possible. When heavy sod, tight 
paving or compact soil is the cause of too little of the normal 
rainfall reaching the roots, artificial means must be used for 
watering. The best method is to keep the sod broken up, but 
when this is not desirable, upright sections of tile may be 
placed at intervals flush with the sod and the necessary water 
furnished by running water into these from a hose. It should 
be remembered that the feeding rootlets are under the edges 
of the branches and not up close to the trunk of the tree. 
The tile should, therefore, be placed at intervals in a circle 
under the tips of the branches. A certain amount of artificial 
fertilizing may also be accomplished through the tiles. When 
the soil contains too much water, the ordinary methods of 
drainage should be employed. 

Reference 

Graves, A. H. Root rot of coniferous seedlings. Phytopathology 5: 
213-217, figs. 1-2. 1915. 

Freezing-to-Death 

Caused by low temperatures 

Many kinds of trees are more or less injured by the freezing 
of the roots. White pine, maple, elm and ash are particularly 
susceptible. 



ROOT DISEASES AND INJURIES 75 

Symptoms. 

The symptoms of freezing-to-death in the roots, as noticed 
in the aerial parts, are general, although somewhat distinctive 
and diagnostic. The primary symptoms can easily be deter- 
mined by examining the roots themselves. Tissue which has 
suffered from freezing-to-death gives no external evidence of 
its condition until some time after it has thawed. Then it ap- 
pears, at first, water-soaked and later, after some disintegration 
processes have set in, it becomes brown. Tissue thus killed is 
soon invaded by the numerous saprophytic organisms in the 
soil and is further disintegrated. 

Severe injury to the entire root system results in the death of 
the tree before summer. The leaves ma}' come out, but re- 
main small and misshapen. Less severe and re-occurring in- 
jury to the roots may result in a varying succession of symptoms. 
One of the most common effects is that of sun-scorch of the 
leaves, and is most common in the pine and maple (see page 22). 
The inability of the remaining healthy roots to provide enough 
water for the leaves to equal the amount transpired on hot days 
results in the wilting and death of the leaves. The entire tree 
suffers then, since the diminution of the leaf-surface makes im- 
possible the manufacture of enough food materials for normal 
growth. Another symptom of root-injury is the production 
of thin foliage at the top, in excurrent trees, and stag-head may 
be the cumulative effect of this condition. 

Cause of frcezincj-to-dcafh. 

In the process of maturing the new tissue formed during the 
summer, the roots are the last part of the tree to attain the con- 
dition necessary to withstand low temperatures without injury. 
A combination of a late warm autumn followed by deep freez- 
ing of the ground may lead to serious root damage. Thus, it 
happens that winter-injury to the roots is exceptionally common 
some winters and rare in others when the temperature falls to 



76 MANUAL OF TREE DISEASES 

even a lower point. The injury caused to the roots is the type 
known as freezing-to-death (see page 12). The water in the 
cells is withdrawn during the formation of ice crystals between 
the cells. As the temperature becomes lower, the physical pull 
incident to ice formation causes a larger amount of water to be 
withdrawn from the living cells than they can endure without 
being killed. Since the root system of most kinds of trees may 
extend from a few inches to several feet below the surface, it is 
natural that shallow-rooted trees will show the first and most 
serious injury provided the minimum temperature for the roots 
of that species is reached. Also, the amount of damage to the 
root system of a given tree depends on whether its roots are 
largely superficial or are found at varying depths. 

Control. 

Winter-injured roots should be uncovered and the dead parts 
pruned off. The wounds should be treated with a wound- 
dressing, and the soil conditions around the tree made con- 
ducive to the rapid regeneration of new roots by fertilizing. 
Mulching may be practiced to protect the soil around sus- 
ceptible trees from freezing deeply. 

Reference 

Stone, G. E. Winter injuries of roots. In Shade trees, character- 
istics, adaptation, diseases and care. Massachusetts Agr. Exp. 
Sta. Bui. 170 : 200-204. 1916. 

Gas-Injury 

Caused by illuminating gas 

Trees are commonly injured by the poisonous effect of illumi- 
nating gas on the roots, when leaks in gas-pipes are not promptly 
repaired. The effect is usually cumulative and the tree may 
show no sign of the injury until some time has elapsed. 



ROOT DISEASES AND INJURIES 77 

Symptoms. 

The symptoms are general in nature, being about the same 
as those produced when any agency causes a gradual death of 
the root system. Partial freezing-to-death of the roots and 
cumulative gas-injury cause similar symptoms. The turning 
yellow or brown of the foliage is a common symptom, probably 
due entirely to the interference with the conduction of the 
necessary supply of water. Later, the living tissues in the root 
and trunk will be found dry and turning brown, showing that 
the lack of water and the poisonous properties of the gas com- 
bined have killed the tissues. At this stage various branches 
die and saprophytic fungi attack the dead bark. The length 
of time which it takes for a tree to die from gas-poisoning de- 
pends entirely on the amount of gas in the soil. Even a 
small quantity of gas present continuously will produce serious 
injury within two or three years. Conifers are much more 
resistant to gas than deciduous trees. At times, the farmer 
recover after the injury becomes apparent, while deciduous 
trees which begin to develop the symptoms of poisoning rarely 
recover, even if the leak is repaired. 

Cause. 

The injury to the roots caused by illuminating gas is probably 
of two kinds : first, true asphyxiation, since the air necessary to 
the roots is replaced by the gas ; and second, the living tissues 
are poisoned. ]\Iany toxic substances are contained in the dif- 
ferent kinds of illuminating gases. These substances when 
dissolved in the soil-water are absorbed into the root and the 
cumulative effect is shown in the death of the cells. 

Control. 

The remedy for gas-injury is to stop the leakage and stir the 
soil until all the gas has escaped. If only a portion of the root 
system and trunk is killed, the tree may be saved by the use of 
surgical methods to remove the dead tissue (see page 3-45). 



78 MANUAL OF TREE DISEASES 

References on Gas-Injury 

Stone, G. E. Effects of illuminating gas on trees. In Shade trees, 
characteristics, adaptation, diseases and care. Massachusetts 
Agr. Exp. Sta. Bui. 170 : 220-228, figs. 93-97. 1916. 

Stone, G. E. Effects of illuminating gas on vegetation. Massa- 
chusetts Agr. Exp. Sta. Ann. Rept. 25:1: 45-60, figs. 1-3. 1913. 

Shoe-String Root-Rot 

Caused bj^ Armillaria mellca (Fries) Quelet 

The shoe-string or honey-mushroom root-rot is common 
throughout the United States on many kinds of coniferous and 
deciduous trees. It has been noted especially on oak, pine, 
chestnut, larch, sycamore, poplar, locust, hemlock, birch, alder, 
maple and many kinds of fruit-trees and shrubs. In some 
sections of the country, especially in south central United States 
and on the Pacific Coast, orchard-trees are commonly affected 
and killed. The disease is most destructive in orchards on 
land recently cleared of oak. In Europe this disease is also 
common on cedar, pine, fir, peach, cherry, olive, grape and 
many other kinds of woody plants. There seem to be no 
definite host relations for the activities of the fungus causing 
this root-rot. It is known to attack the potato. 

No very accurate facts are available as to the parasitic po- 
tentialities of the honey-mushroom. It occurs every where . on 
stumps and dead wood and is commonly found on trees in poor 
health or badly wounded. The relation between the decline of 
the tree and the attack of this fungus is hard to determine. 
However, abundant evidence is at hand that young thrifty 
trees in the forest and orchard are often killed, when there is 
no doubt that the honey-mushroom Avas directly and primarily 
the cause of the decay of the roots. It is, therefore, reasonable 
to expect that on further investigation this root-rot will be 
fully shown to be a primary cause of the decline and death of 
the trees. In many cases, however, it may play only a sec- 



ROOT DISEASES AND INJURIES 



79 



ondary part. The fungus is so prevalent as a saprophyte that 
its occurrence as a wound parasite and root-rotting fungus on 
trees is not surprising. 

Symptoms. 

The bark and wood of the roots are affected and the li\'ing 
tissues destroyed. The decay may also extend up into the 
bark and sap wood of the h)wer 



part cf the trunk (Fig. 6) 
Trees with the root system 
partially destroyed display 
general symptoms of decline 
and poor health, such as dead 
limbs, scant}' and light green 
foliage, and but little annual 
growth. In conifers a large 
amount of resin exudes from 
the base of the tree and ac- 
cumulates as a hard cake (Fig. 
6). The time from the first 
signs of decline to final death 
may extend over a period of 
three or four or more years. 
There are many diagnostic 
symptoms by which this root- 
rot may be identified. The 
mycelium of the causal fungus 
when growing in the soil out- 
side the roots is bound to- 
gether in long round, black 
strands somewhat resembling 
shoe-strings. These black strands may be found growing 
attached to the bark of the roots and trunk or running 
through the soil for long distances away from the affected 





Fig. G. 



Whits pine killed by shoe- 
string root-rot. 



80 



MANUAL OF TREE DISEASES 



roots (Fig. 6). The strands may be traced to points at which 
they enter the roots. At these points the white myceUum in- 
side the black strands spreads out and runs in all directions in 
the bark and sapw^ood. Thin white sheets of mycelium are 
found in the cambium region (Fig. 6). The tissues of the 
cambium and bark are destroyed and replaced by the white 
sheets. The mycelium also penetrates the medullary-rays and 
sapwood and causes a wet white rot. After the bark is killed, 
the black shoe-strings are formed abundantly between the 
bark and wood. They anastomose in all directions and form 

a network. The decayed 
area of sapwood and bark 
is bordered by a brown 
zone. 

The fruiting-bodies of the 
fungus are honey-colored 
toadstools or mushrooms. 
They appear on the sides of 
the trunk, exposed roots or 
directly fnjm the ground. 
Close examination will show 
their attachment to the 
black shoe-strings (Fig. 7). 
The toadstools occur in 
clusters, attached to one another at the base of the stalks. 
The stalks are somewhat swollen at the base and have a fragile 
collar just beneath the cap. The upper surface of the cap 
is smooth and yellowish or brownish. The under surface is 
composed of radiating pendent plates or gills of the same 
color (Fig. 8). 

Cause. 

The shoe-string root-rot of trees is caused by the mushroom, 
Armillaria mellea. The spores are borne on the sides of the 




Fig. 7. — Young toadstools of Armillaria 
mellea attached to shoe-strings. 



ROOT DISEASES AND INJURIES 



81 



gills or plates on the under surface of the fruiting-body (Fig. 8). 
The tree-roots are infected in several ways. The spores may 
cause infection through wounds at the base of the tree or in ex- 
posed roots. The black strands running through the soil may 
also penetrate the 
bark of the roots. 
In this manner the 
fungus spreads 
through the soil 
from the roots of 
one tree to another. 
This mode of infec- 
tion accounts for 
the occurrence of 
circular areas of dis- 
eased trees. Since 
the fungus also com- 
monly occurs as a 
saprophyte on dead 
wood, the fruiting- 
bodies are produced 
in great abundance 
on prostrate trunks 
and on old stumps 
for several years 
after the affected 
tree is dead. 




Fig. 8.- 



Mature fruiting-body of Armillaria mcllca, 
showing gills on under surface. 



Control. 

Root diseases are difficult to control since the condition of the 
roots cannot be readily ascertained. By destroying the toad- 
stools and remo\'ing the diseased roots or parts of roots, the 
individual tree may be saved. In the orchard or forest, dis- 
eased trees or groups of trees may be surrounded by isolation 



82 MANUAL OF TREE DISEASES 

trenches, a foot or two deep. All roots bridging the trench 
must be removed and the trench kept free of debris and fruit- 
ing-bodies. The trench must be dug far enough away from 
the affected trees to insure the absence of diseased roots out- 
side of the area to be isolated. 

References 

Long, W. H. The death of chestnuts and oaks due to Armillaria 

mellea. U. S. Dept. Agr. Bui. 89 : 1-9, pis. 1-2. 1914. 
Schrenk, Hermann von, and Spaulding, P. Root-rots. In Diseases 

of deciduous forest trees. U. S. Dept. Agr. Bur. PL Ind. Bui. 

149 : 22-24. 1909. 
Hesler, L. R., and Whetzel, H. H. Armillaria root-rot. In Manual 

of fruit diseases, pp. 96-102, figs. 26-27. 1917. 
Hartig, R. Agarieus melleus L. In Die Zersetzungserscheinungen 

des Holzes etc., pp. 59-62, pi. 11. 1878. 
Hartig, R. Agarieus (Armillaria) melleus L. In Wichtige Krank- 

heiten der Waldbaume, pp. 12-42, pis. 1-2. 1874. 
Lawrence, W. H. Root diseases caused by Armillaria mellea in the 

Puget Sound coimtry. Washington Agr. Exp. Sta. Bui. (special 

series) 3: 1-16, figs. Vs. 1910. 
Piper, C. v., and Fletcher, S. W. Root diseases of fruit and other 

trees caused by toadstools. Washington Agr. Exp. Sta. Bui. 

59 : 1-14, figs. 1-5. 1903. 
Home, W. T. The oak fungus disease of fruit trees. California State 

Com. Hort. Monthly Bui. 3 : 275-282, figs. 79-81. 1914. 
Home, W. T. Fungous root rot. California State Com. Hort. 

Monthly Bui. 1 : 216-225, figs. 85-91. 1912. 
Home, W. T. Oak fungus or Armillaria mellea in connection with 

nursery stock. California State Com. Hort. Monthly Bui. 4 : 

179-184, figs. 31-33. 1915. 
Barss, H. P. Musliroom root rot of trees and small fruits. First 

Biennial Crop Pest and Horticultural Report (Oregon Agr. Exp. 

Sta.) 1911-1912 : 226-233, figs. 23-38. 1913. 



jMycorhizas 

Caused by various species of fungi 

An interesting type of parasitic relation between certain 
species of fungi and the living roots of many kinds of trees con- 



ROOT DISEASES AND INJURIES 83 

sists in the development of mycorhizas. These strnctures 
probably in no manner interfere sufficiently with the growth of 
the roots to cause any damage. Trees with mycorhizas on the 
roots cannot be distinguished from those without by any above- 
ground symptoms. A short account of them is, however, of 
interest since the structures are now generally considered to 
represent a diseased condition of the roots and not a true type 
of symbiosis or mutual-advantage relation, as was previously 
believed by many. 

The term mycorhiza is used to signify the infected root and 
the mycelium of the fungus, as an association of two distinct 
but physiologically interdependent tissues. This usage is thus 
similar to the use of the term lichen, the formation of which 
requires the association of certain algae and fungi to form the 
characteristic structures known as lichens. Mycorhizas are 
of two types : ectotrophic, when the mycelium forms a mantle 
or sheath aroiuid the root-tip and penetrates the tissues by inter- 
cellular (existing between the cells) threads of the mycelium ; 
and endotrophic, when the mycelium is within the tissue and is 
largely intracellular (within the cells). Recent investigations 
have shown that hickory, oak, basswood, birch, larch, poplar 
and beech commonly show ectotrophic mycorhizas, and species 
of maple, butternut and horse-chestnut have endotrophic forms. 
Elm and species of willows were found not to have mycorhizas. 
This list is by no means complete, but represents the species 
reported in the reference given below. With the exception of 
this work, little is reported in American literature on mycorhi- 
zas. European literature on the subject, however, is abundant. 

Both types of mycorhizas are annual. The mycelium of the 
species of fungi capable of forming mycorhizas penetrates the 
young root-tips in the summer. The association with the root- 
tissues is rapidly formed and food materials are obtained by the 
fungus. Later, the fungus may produce a growth of mycelium 
in the soil in the autumn, in which case fruiting-bodies are 



84 MANUAL OF TREE DISEASES 

formed on the surface of the ground. Several kinds of toad- 
stools and puff-ball fungi have been proved to be mycorhizal 
fungi. Ectotrophic mycorhizas are recognized by the short, 
stubby, lateral rootlets, which are covered with the fungus 
mantle and may be white, brown, yellow or red. The same 
tree may show several different kinds of mycorhizas, each caused 
by a different species of fungus. When the mycorhizal pro- 
duction is profuse, whole clusters of the stubby roots may form 
a coral-like structure. The endotrophic mycorhizas on maple 
roots form bead-like swellings, often in chains. The mycelia 
of some endotrophic mycorhizas have been found to produce 
fruiting-bodies, which place them in the genus Phoma. 

Reference 

McDougall, W. B. On the mycorhizas of forest trees. Amer. Jour. 
Bot. 1 : 51-74, pis. 4-7, fig. 1. 1914. (Bibliography given.) 

Roots Parasitized by Flowering Plants 

Several species of flowering plants attach their root-like 
organs to the roots of other plants and trees, and draw a certain 
amount of food materials from them. All degrees of para- 
sitism are found, from the species of the broom-rape family 
(Orobanchacese) which develop no leaves or chlorophyl and 
are entirely dependent on other plants for food, to those types 
which develop normal green foliage above ground, and some- 
times grow without forming any attachments to the roots of 
other plants. Certain species of Comandra have been found 
to be of the latter type. Their roots normally develop disc- 
like attachments, which connect the tissues of the Comandra 
roots with the roots of various other plants. They have been 
found attached to the roots of the following trees : maple, 
birch, chestnut, poplar, oak and sumac. Very little damage is 
done to the tree. Examples of the former type, mentioned 



ROOT DISEASES AND INJURIES 85 

above, where all the food materials required by the plant are 
obtained through the connected roots, include the common 
beech-drop (see page 108), indian-pipe and many other plants 
belonging to various families of the flowering plants. 

References 

Hedgcock, G. G. Parasitism of Comandra umbellata. Jour. Agr. 

Res. 5 : 133-135. 1915. 
Harshberger, J. W. Vegetal agents of disease. In A text-book of 

mycology and plant pathology, pp. 298-306, figs. 117-123. 1917. 



CHAPTER V 
ALDER DISEASES 

Several native species of alder (Alnus) are common forest- 
trees in the Northwest and Rocky Mountain region. They 
grow in river-bottom lands and on mountain sides. In eastern 
United States, the European alder is used as an ornamental and 
in some localities has become naturalized. 

The alder is particularly subject to wood-rot diseases. The 
common white and the brown checked wood-rots often cause 
death by destroying the sapwood. The leaf-blisters, deforma- 
tion of the catkins and catkin powdery mildew attract attention 
when they occur, but they do only slight damage to the tree. 
The alder also is one of the non-leguminous plants on which 
the nitrogen-fixing bacteria form root-tubercles. The several 
shrubby species of alder are subject to the same diseases as the 
larger trees. 

Powdery Mildew of Catkins 

Caused by Erysiphe aggregala (Peek) Farlow 

In northeastern United States, the female catkins of alder are 
often covered with a powdery mildew. A similar, if not identi- 
cal, fungus attacks the twigs of alder in Europe. The catkins 
are covered with a white or yellowish coating of mycelium which 
later may be dotted with clusters of small black fruiting-bodies. 
The life history and methods of control of the powdery mildew 
fungi are discussed on page 37. Two other species of the pow- 
dery mildews occur on alder leaves. 

86 



ALDER DISEASES 87 

Catkin-Deformation 

Caused by Exoascus amentorum Sadebeck 

The catkins of several species of alder are affected by this 
disease. The same disease is common in Europe. The scales 
of the fertile catkins become much enlarged and project as 
curled, reddish tongues. Later they are covered by a white 
glistening coat of the fruiting structures of the parasite. The 
mycelium is perennial in the twigs. Practically no damage is 
done to the tree. If preventive measures are desired, the prun- 
ing of the diseased parts should eventually eliminate the 
difficulty. 

Brown Checked Wood-Rot 

Caused by Poly par us sulphurcus Fries 

The alder is one of the many deciduous trees commonly af- 
fected by the brown checked wood-rot. Chief among the other 
kinds affected are oak, chestnut, walnut, butternut, maple and 
locust. The causal fungus enters through some wound where 
the heartwood is exposed. The heartwood and sap wood are 
both decayed and become like red-brown charcoal. Thin 
yellowish sheets of mycelium, within concentric and radial 
checks, divide the decayed wood into small punky cubes. The 
fruiting-bodies emerge, usually, from old branch wounds and 
consist of many overlapping shelves forming a large, more or 
less globose mass. The upper surfaces of the shelves are orange- 
red, while the under surfaces are sulfur-yellow. For further de- 
tails concerning this wood-rot see under oak diseases, page 247. 

Common White Wood-Rot 

Caused by Fomcs igniarius Fries 

Alders are destructively affected in Europe by the common 
white wood-rot. In the United States such trees as beech, 



88 MANUAL OF TREE DISEASES 

poplar, willow, maple, butternut, walnut, oak and hickory are 
the most commonly affected by this wood-rot. Specific men- 
tion of this disease in alder is less frequent in this country be- 
cause of the slight economic importance of the species of alder. 
For a description of the symptoms of the common white wood- 
rot, see under poplar diseases, page 305. 

Root-Tubercles 

Caused by Bacillus radicicola Beijerinck 
The roots of alder commonly show large clusters of short 
stubby roots. These abnormal roots represent a diseased con- 
dition by which the alder benefits. The dwarfed roots are in- 
habited by the same bacterium which causes the root-tubercles 
of clover, bean, cowpea, locust and other leguminous plants. 
The bacteria gain entrance to the young lateral rootlets by way 
of the root-hairs. They multiply within the cells of the cortex 
of the root and stimulate this tissue to over-growth. They 
live parasitically and obtain their food materials from the proto- 
plasm and cell sap of the alder roots, but they do not kill the 
cells they inhabit. These bacteria take the free nitrogen gas 
from the air and combine it with other substances. After this 
is accomplished, the alder roots eventually receive this combined 
nitrogen and the tree uses it in its metabolic processes. In this 
way large quantities of nitrogen are obtained indirectly from 
the air by the alder. The higher plants cannot utilize nitrogen 
gas from the air and the plants which are parasitized by the 
nitrogen-fixing bacteria are thus greatly benefited. Such a 
mutual-benefit relation between the alder and the bacteria is 
known as symbiosis, although strictly speaking the bacteria are 
parasitic even though they do not cause the death of the root- 
tissues. 

Reference 

Spratt, Ethel R. The morphology of the root tubercles of Alnus and 
Elaeagnus, and the polymorphism of the organism causing their 
formation. Ann. Bot. "26 : 119-128, pis. 13-14. 1912. 



. CHAPTER VI 
ARBOR-VITiE DISEASES 

Two species of arbor-vitse (Thuja) are common forest-trees 
in northeastern and northwestern United States. They occur 
in moist river-bottom lands and along mountain streams. The 
western arbor-vitse grows to a much larger tree than the eastern 
species. Both species are extensively used as ornamentals. 

The eastern arbor-vitse is especially free from diseases. 
The wood and roots of the living tree are seldom decayed 
and no leaf or twig-diseases of any importance are known. 
The western arbor- vitae, on the other hand, is destructively 
attacked by a leaf-fungus. The younger trees may be killed 
outright. In the nursery, arbor-vitse is subject to a common 
blight which also affects juniper. Ornamental arbor-vitse 
seldom suffer from fungous diseases but frequently are injured 
by freezing-to-death, sun-scorch and other general troubles 
(see index). 

Seedling-B light 

Caused by Phoma sp. 

At least three species of Thuja, including the eastern and 
western arbor-vitse, are affected by this seedling-blight. The 
same disease is common on juniper. Young arbor-vitse trees 
up to four years old are affected in the same manner as juniper 
(see page 190). Cankers are formed which girdle the stem, 
causing the plants to die. The disease often becomes epiphy- 
totic and causes serious losses in nursery-beds. Control 
measures have not been determined. 

89 



90 MANUAL OF THEE DISEASES 

Leaf-Blight 

Caused by Kcithia ihujina Durand 

The leaf-blight or black leaf-spot of western arbor-vitse is 
common and destructive, especially to young trees, throughout 
its range in northwestern United States. In dense stands 
and in localities where humid conditions prevail, this disease 
causes the death of a large percentage of the seedlings less than 
four years old. In late summer the lower branches of older 
trees when affected by this blight aj^pear as if scorched by fire. 
In some localities the foliage of the upper parts of the trees 
also may be affected. This is, however, essentially a disease 
of seedlings. The affected parts are those which are covered 
by snow until late in the season. 

Symptoms. 

In spring and summer the affected leaves show from one to 
three more or less circular brown cushions bursting through the 
epidermis. Later these bodies turn black. The affected leaves 
die and turn brown in late summer. The tw^igs bearing the 
brown leaves also fall, leaving the branches bare. In autumn 
the black bodies in the older leaves often fall out, leaving holes, 
and these leaves turn gray. 

Cause. 

The leaf-blight or black leaf-spot of the western arbor-vitse 
is caused by the fungus Keithia thiijina. This fungus is closely 
related to the tar leaf-spot fungi of maple and willow and the 
black-specked leaf-spot fungus of maple. The black fruiting 
bodies on the leaves crack open, irregularly, and expose the 
ascospore-bearing surface within. The ascospores are wind- 
blown and infection usually occurs in the autumn. Moist 
weather is necessary for the discharge of the spores. 



ARBOR-VITM DISEASES 91 



Control. 



Preliminary experiments seem to indicate that soap-bordeaux 
mixture applied to young trees, every ten days or oftener in 
the autumn, will greatly reduce the amount of infection. 

References 

Weir, J. R. Keithia thujina, the cause of a serious leaf disease of the 
western red cedar. Phytopathology 6 : 360-363, figs. 1-2. 1916. 

Durand, E. J. The genus Keithia. Mycologia 5:6-11, pi. 81. 
1913. 

Brown Pocket Heartwood-Rot 

Caused by Fomes roseus Fries 

There are few statements in literature concerning the fungi 
which cause the decay of the wood and roots of arbor-vitae. 
Mention is made of brown pockets of decay in wood of the trunk 
which are probably due to Fomes roseus. This fungus causes 
a heartwood-rot of fir, juniper, larch, spruce, pine, and hemlock. 
The fruiting-bodies have been found also on a few deciduous 
trees. The decay caused by this fungus is described under 
juniper diseases (page 204). The color of the decayed wood 
varies from dark to a lighter brown according to whether the 
normal wood is deeply colored or not. In some cases the 
similarity between the effects of Fomes roseus and Polyporus 
Schiceinitzii may lead to confusion as to which is the true cause 
of the rot, unless the sporophores are found attached to the 
tree in question. 

Red-Brown Root- and Butt-Rot 
Caused by Polyporus Schweinitzii Fries 

This is one of the few wood-rots of conifers which occurs 
in arbor-vitse. Pine, fir, spruce, hemlock and larch are seri- 



92 MANUAL OF TREE DISEASES 

ously damaged by this root disease throughout their range. 
The wood of the affected roots is at first yellowish and cheesy 
but later it becomes red-brown and brittle. The rot sometimes 
extends up into the trunk. A more complete description of 
this disease is given under pine diseases, on page 294. 



CHAPTER VII 
ASH DISEASES 

Several species of ash (Fraxinus) are common forest-trees 
in most parts of the United States. White, green and black 
ash are the important timber-trees. These are common 
throughout eastern and central United States. The same 
three species mentioned above are frequently used for shade 
and ornament. 

Ash is exceptionally free from destructive diseases. The 
rust of the leaves occurs sporadically and may assume an 
epiphytotic nature. Little damage is caused to the trees, 
however, unless defoliation occurs two or three years in suc- 
cession. Several parasitic fungi cause leaf-spots on ash (see 
page 29). Only one wood-rot is described as important in ash. 
This disease is rarely found in the East but is destructive on 
the western limits of the white ash. The slow growth which 
the ash makes in that region seems to predispose the trees to 
this disease. Where the trees grow more rapidly, they are 
seldom affected. The roots of ash frequently are killed by 
low temperature (see page 74). 

Leaf- and Twig-Rust 

Caused by Puccinia fraxinata (Link) Arthur 

The leaf- and twig-rust of red, green and possibly other 
species of ash is striking because of its effect on the leaves and 
twigs and its epiphytotic nature. It is common, at least in 
eastern and central United States, but varies greatly in abun- 

93 



94 



MANUAL OF TREE DISEASES 




dance from year to year. In central Iowa and eastern Nebraska, 
this disease was so abundant in 1885 that it was difficult to 
find leaves not affected. The next two summers scarcely any 
of the rust could be found. In 1888 it was again abundant 
in the same region. An epiphytotic of this 
disease was reported in 1887 around Washing- 
ton, D. C, with very little of the rust in 
that region the next j-ear. No recent reports 
of such outbreaks have been published. 

Symjitoms. 

This rust causes swellings w^hich are irregu- 
lar or more or less globose. They appear on 
the petioles of the leaves and on the twigs 
(Fig. 9). Swollen areas are also formed on 
the leaves which are much distorted. Soon 
after the swellings are formed they are covered 
by numerous blister-like protrusions, which 
break open, leaving cup-shaped areas filled 
Fig. 9. — Ash-rust ^^.j^j^ yellowish powder (Fig. 9). This stage 

Fruiting-bodies of '^ • n -i i i 

of the rust is called the cluster-cup stage. 

The yellow powdery material is composed of 
the spores (seciospores) of the fungus. The distortion of the 
petioles and leaves, covered with the yellow cluster-cups, make 
this disease conspicuous. 

Cause. 

Ash-rust is caused by Puccinia fraxinata. This fungus 
requires two kinds of host plants to complete its life history. 
The spores produced in the cluster-cups on the ash do not 
reinfect the ash, but must find lodgment on the marsh or 
cord-grasses (Spartina) in order to continue their develop- 
ment. On the grass plant, spores are produced which infect 
the ash the next spring. 




causal fungus 
swollen petiole. 



ASH DISEASES 95 

Control. 

The disease will probably not be noticed until the cluster- 
cups have broken open and shed their spores. It would then 
be of no avail to destroy the diseased parts of the ash, since 
the spores have already been distributed. If practicable, ash 
trees should not be grown in the vicinity of marshy land where 
the Spartina grass-hosts grow. In the absence of the grass- 
host, so far as the life history of this rust is known, there is 
no chance of infection of the ash. 

White Heartwood-Rot 

Caused by Fonies fraxinophilus Peck 

White ash is commonly affected by this heartwood-rot in 
parts of Iowa, Missouri, Kansas and Oklahoma, on the wes- 
tern limit of growth of this species. The disease is rarely 
found in eastern United States. West of the Mississippi 
River, where the white ash attains only three-fourths its normal 
size, ninety per cent of the trees are often found diseased ; a 
fact which suggests some correlation between the condition of 
the trees in this region and their apparent greater susceptibilit3^ 
The slow rate at which wounds heal, however, may be the 
predisposing factor which accounts for the greater abundance 
of the disease. Trees of all ages and especially those over 
seven inches in diameter are affected. 

Symiitoms. 

The rotted area as seen in cross-section of the trunk is very 
irregular in outline and often is more extensive on one side of 
the tree. The normal wood of the white ash is light yellow. 
In the first stages of decay, the wood is stained brownish. Later 
the affected wood becomes whitish and is surrounded by a 
brown zone where the decay is extending into the normal 
wood. The spring-wood of each annual ring becomes 



96 MANUAL OF TREE DISEASES 

white, while for a time the summer-wood remains brownish. 
Shortly, however, the summer-wood becomes whitish and in 
the final stages of the decay the wood is soft and crumbly. 

The perennial sporophores of the causal fungus are formed 
at old branch wounds. They are usually small bracket-shaped 
bodies. The upper surface is hard, dark brown or black and 
marked by concentric folds. The under surface is velvety, 
straw-colored and covered with large circular pores. The 
inner structure of the fruiting-body is white or light brown, 
according to its age. A new layer of tubes is added to the 
lower surface each year. 

Cause. 

The white heart wood-rot of white ash is caused by Fomes 
fraxinophilus. This fungus is rarely found on any other tree. 
Living green ash trees have been observed with the fruiting- 
bodies on them and it is possible that a rot of similar nature as 
that caused in white ash may be found in green and other ashes. 
The spores borne within the tubes on the under surface of the 
fruiting-body fall out of the pores and are blown about by the 
wind. When they find lodgment on exposed heartwood of the 
white ash, a new mycelium may be initiated. The initial 
stages in the decomposition of the fibers result in a brown 
liquid which stains the wood. Later this colored liquid disap- 
pears and the mycelium delignifies the cell-walls and dissolves 
most of the cellulose. The fungus is not known to occur as a 
saprophyte. For further details concerning the life history and 
control of the wood-rotting fungi of living trees, see page 64. 

References 

Schrenk, Hermann von. A disease of the white ash caused by Poly- 
porus fraxinophilus. U. S. Dept. Agr. Bur. PI. Ind. Bui. 32 : 
1-20, pis. 1-5, fig. 1. 1903. 

Schrenk, Hermann von, and Spaulding, P. White heart-rot of ash 
caused by Fomes fraxinophilus. In Diseases of deciduous forest 
trees. U. S. Dept. Agr. Bur. PI. Ind. Bui. 149 : 4G-47. 1909. 



CHAPTER VIII 

BALD CYPRESS DISEASES 

The bald cypress or Taxodium is an important timber-tree 
in southern and southeastern United States. It is frequently 
used as an ornamental. The pecky heartwood-rot is the only 
known disease of any importance which attacks this tree. 

Pecky Heartw^ood-Rot 

Caused by Fomes geotropus Cooke 

The pecky heartwood-rot of bald cypress is a common disease 
and is recognized by every one who handles cypress timber. 
The disease is also known by the names peggy-, botty- and bot- 
cypress and the peck or puck of cypress. Bald cypress trees 
throughout their range are more or less affected by this disease. 
It seems, however, to be more common and destructive in the 
extreme southern states. It has been estimated that one-third 
of the cypress timber available is damaged by this wood-rot. 
Older trees are most often affected and, in many cases, the tops 
of the trees are decayed without damage to the principal timber 
portion. The number of trees showing more or less peckiness 
has been found to vary from practically 100 per cent of the stand 
in Florida and Louisiana to smaller percentages toward the 
northern limits of the range of cypress in North Carolina, In- 
diana and IMissouri. Since the pecky wood has been found to 
be practically as durable as the normal unaffected wood, it is 
used for rough lumber and as ornamental finishing for rustic 
H 97 



98 MANUAL OF TREE DISEASES 

effects. The general worm-eaten appearance of the pecky 
wood leads to the impression that the injury is due to wood- 
boring insects. 

Symptoms. 

The tops of trees one hundred and twenty-five years old or 
older are frequently affected. The rot is also found in the butts. 
Younger trees are rarely affected by this disease. The first 
indications of the rot are localized areas yellowish in color and 
about one-fourth inch wide and several inches long. The wood 
between the yellowish areas is unchanged. Decomposition of 
the wood elements in the yellow areas proceeds until definite 
cavities are formed. These cavities are partially filled with a 
yellow-brown powder and occasionally white mycelium and 
fibrous masses of partially decayed wood are found mixed with 
the brown powder. Sometimes the pockets are found entirely 
empty. The pockets extend lengthwise with the grain of the 
wood and are about one-fourth of an inch wade and four or five 
inches long. They are very smooth-walled and nearly cylindri- 
cal and blunt ended. Peckiness is usually confined to the upper 
part of the trunk and older branches. In very old individuals, 
the wood at the base of the tree may be affected. The pockets 
are not always found at the center of the tree but may be located 
on one side or extend around the trunk leaving the center un- 
affected. The pockets may be several inches apart and scat- 
tered through the cross-section; or densely aggregated in the 
older wood or in certain annual rings. The badly affected trees 
are not appreciably weakened and are rarely blown over. The 
wood between the pockets is slightly darker in color than the 
normal wood but it is unchanged structurally. Recently it has 
been learned that the hollows sometimes found in the butts or 
trunks of cypress seem to be due to the complete destruction 
of the wood between the pockets. 

The fruiting-bodies of the fungus causing the peckiness are 



BALD CYPRESS DISEASES 99 

rarely found. They also occur on many kinds of deciduous 
trees and may be associated with wood-rots in these trees. 
The perennial fruiting-bodies are produced on the lower part of 
the trunk and are thick, woody, shell-shaped bodies, measuring 
■from three to six by five to ten inches. The upper surface is 
marked with numerous concentric ridges. It is straw-colored 
and slightly hairy or smooth. The under surface is rose-colored 
at first but becomes darker with age. The pores are small. 
The inner substance of the fruiting-body is corky and yellowish 
brown. 

Cause. 

The pecky heart wood-rot of bald cypress is caused by Fames 
geotropus. The spores from the tubes on the under side of the 
fruiting-body infect broken branches in the top of the tree. 
From these points of entrance, the mycelium grows downward 
into the heartwood. The mycelium becomes abundant in cer- 
tain centers. At these places the yellow areas appear and finally 
the pockets are formed. From the first formed yellow areas, 
strands of the mycelium penetrate the normal wood in all direc- 
tions without destroying it. At some distance from the original 
yellow areas, new centers of luxuriant mycelial growth originate 
and pockets are formed. In this way the wood may become 
pecky in older trees throughout the entire length of the trunk. 

Pecky cypress is peculiar in the fungus usually ceasing its 
activity with the formation of the pockets. The cells imme- 
diately surrounding the pockets are filled with a brown humus 
compound, which is believed to inhibit the further development 
of the mycelium. The wood between the pockets is normal and 
no further decay takes place when the pecky timber is placed 
under the various extreme conditions conducive to decay. 
Normal cypress and pecky cypress timbers are eciually resist- 
ant to decay and are the longest lived of the timbers of this 
country. 



100 MANUAL OF TREE DISEASES 

For further details concerning the general life history and 
control of the wood-rot fungi, see page 64. 

Reference 

Schrenk, Hermann von. A disease of Taxodium distichum known as 
peckiness, also a similar disease of Libocedrus deeurrens known 
as pin-rot. Missouri Bot. Gard. Ann. Kept. 11 : 23-77, pis. 1-6. 
1900. 



CHAPTER IX 
BASSWOOD DISEASES 

Tpte several species of basswood or linden (Tilia) are 
common in eastern and central United States. These trees, 
as well as several European basswoods, are extensively used as 
shade and ornamental trees in the same region. 

No serious diseases affect the basswood. Several leaf-spots 
and one powdery mildew affect the leaves occasionally. The 
sapwood may be destroyed and the trees killed where wood- 
peckers damage the bark and allow fungi to enter. In the 
South the roots of the basswood are often decayed by a fungus 
which is common in heavy soils. 

Powdery Mildew 

Caused by Uncinula Clintonii Peek 

This powdery mildew fungus attacks the leaves of basswood 
in northeastern and north central United States. The myce- 
lium is visible on both sides of the leaf, causing diffused 
powdery white patches. Small black fruiting-bodies which are 
just visible to the unaided eye are scattered over the whitish 
area. This species, although indistinguishable from other pow- 
dery mildew fungi, except by microscopic characters, is so far 
the only one reported on basswood leaves. The life histories 
and methods of control of powdery mildew fungi are discussed 
on page 37. 

101 



102 



MANUAL OF TREE DISEASES 



Leaf-Spot 

Caused by Cercospora tilice Peck 

The leaves of the basswood are often affected by this disease. 
Large brown dead areas are formed at the tip or along the mar- 
gin of the leaf (Fig. 10). A broad yellowish border surrounds 




Fig. 10. — Leaf-spot of basswood. 

the spot. The fruiting bodies of the causal pathogene are in- 
conspicuous. For the general life history and control of leaf- 
spot fungi, see page 33. 



BASSWOOD DISEASES 103 

White Sapwood-Rot 

Caused by Collybia velutipcs Curtis 

This sapwood-rot is occasionally found in basswood, horse- 
chestnut and other deciduous trees. The sapwood becomes 
soft and decayed, and the decline and death of the tree gradually 
results. Injuries in the bark caused by woodpeckers and other 
birds are often found to predispose the trees to attack. The 
sporophores of the causal fungus emerge in clusters from 
wounds in the bark. They are small toadstools, with yellow 
or brownish tops and gills. The bases of the stems are cov- 
ered with a dark brown velvety growth of hairs. For the gen- 
eral life history and control of the wood -rot fungi, see page 64. 

Reference 

Stewart, F. C. Trunk rot. ?Collybia velutipes Curt. (Horse chest- 
nut). In Notes on New York plant diseases, 1. New York Agr. 
Exp. Sta. Bui. 328:361. 1910. 

Southern Root-Rot 

Caused by Ozonium sp. 

A great variety of plants in the South, including many trees, 
are attacked by a root parasite, which is peculiar in that no 
spores of any type have been found and it is known only by the 
mycelium. Cotton and sweet potatoes are among the field 
crops seriously affected. Several kinds of trees, especially bass- 
wood, elm, Cottonwood (poplars) and mulberry, are known to 
be attacked and the roots killed. Plum trees and closely re- 
lated species and varieties are more or less immune. The second- 
ary symptoms are those which accompany any root-rot. The 
leaves wilt and die when the roots are no longer able to function 
in furnishing sufficient water and food materials. The roots 
are invaded by the mycelium and the living tissues are killed. 



104 MANUAL OF TREE DISEASES 

Abundant growths of the sterile myceUum, which is coarse, 
loosely matted and reddish brown, cover the affected roots. It 
also grows over decaying sticks and other matter on the surface 
of the ground. The mycelial growth has the appearance of a 
quantity of tangled hair. 

The mycelium spreads through the soil and is transported in 
various ways by cultivating tools. It is said to display excep- 
tionally destructive tendencies in wet, badly drained soils and 
during rainy periods. Loosening the soil, deep plowing and 
drainage are said to reduce losses by retarding the spread of the 
mycelium in the soil. 

Reference 

Gralloway, B. T., and Woods, A. F. Southern root-rot. In Diseases 
of sliade and ornamental trees. U. S. Dept. Agr. Yearbook 1896 : 
248-249. 1897. 



CHAPTER X 
BEECH DISEASES 

The beech (Fagus) is a common tree throughout eastern and 
central United States. The American and different varieties 
of the European beech are often used as ornamentals. 

No serious diseases of the leaves of beech are known. Several 
fungi cause leaf-spots occasionally and a sooty mold fungus often 
occurs on the leaves (see pages 27 and 41). The beech is 
subject, however, to several wood-rot diseases. The yellowish 
sapwood-rot and common white wood-rot are very destructive 
in the forest. The roots are parasitized by the flowering plant 
commonly known as beech-drop. This parasite, however, does 
not cause any damage. 

Yellowish Sapwood-Rot 

Caused by Fomes fomentarius Fries 

This sapwood-rot is common on beech, yellow birch and to 
a lesser extent on other deciduous trees of northeastern and 
north central United States. The fungus causing the decay is 
also an important and rapid timber-destroyer throughout its 
range. Where beech or birch is predominant and any unusual 
amount of injury has occurred because of fire or limb breakage, 
this sapwood-rot is found in great abundance and causes large 
losses in timber values. It is also a common disease in Europe. 

Symptoms. 

The decay produced is distinctly a sapwood-rot at first, 
starting in the outer layers next to the bark. As a result of 

105 



106 



MANUAL OF TREE DISEASES 



the activities of the fungus, the wood is reduced to a soft, Hght 
yellowish punk. Black lines are formed between the decaj^ed 
and unaffected wood in places, or they may persist in the com- 
pletely decayed portion. The rot extends into the heartwood 
toward the center of the tree. Where splits or checks occur in 

the decayed portion, a chamois- 
like sheet of closely woven yel- 
lowish mycelium is formed 
which fills the space and can 
with care be removed in large 
pieces. Trees are usually first 
affected in the upper half. 

The sporophores or punks of 
this fungus, which are formed 
on the trunks of affected trees, 
usually occur in large numbers 
on each tree, the number vary- 
ing with the extent of the de- 
cay. The sporophores are not 
confined to old branch wounds 
as usually is the case with 
heartwood-rotting fungi, but 
emerge from apparently unin- 
jured bark of the trunk. They 
are easily recognized, being dis- 
tinctly hoof-shaped and light to 
dark gray on top. The lower 
surface is light brown, with 
rather large regularly arranged circular pores. Both surfaces 
are smooth and velvety when young. A new layer of tubes is 
added each year, which extends beyond the previous year's 
growth, producing an arched ridge (Fig. 11). The margin 
of the sporophore is rather thin and the tube-surface is some- 
what concave. 




Fig. 11. — Frui ting-body of Fames 
fomentarius. 



BEECH DISEASES 107 

Cause. 

The common yellowish sapwood-rot of beech and yellow birch 
is caused by Fomes fomentarius. Spores drop out of the tubes 
on the under side of the sporophores and are blown away. Any 
wound in the bark exposing the sapwood furnishes a suitable 
place for these spores to germinate and start a new mycelium. 
The elements of the wood are largely destroyed, leaving a loose 
mass of easily crumbled fibers. The effect of such a sapwood- 
rot on the life of the tree is more serious and quickly destructive 
than when equally extensive areas of the heartwood are de- 
stroyed. The decay of the sapwood interferes with the trans- 
portation of food materials and water, and thus produces the 
same effect as mechanical girdling. After the tree dies, the 
fungus works very rapidly as a saprophyte and destroys the re- 
maining wood. For further details concerning the life history 
and control of the wood-rotting fungi of living trees, see page 64. 

Reference 

Sehrenk, Hermann von, and Spaulding, P. Decay caused by Fomes 
fomentarius. In Diseases of deciduous forest trees. U. S. Dept. 
Agr. Bur. PI. Ind. Bui. 149 : 50-51. 1909. 

Common White Wood-Rot 

Caused by Fomes igniarius Fries 

This white wood-rot is a common and destructive disease of 
beech. Many other kinds of deciduous trees are subject to the 
same disease, principally poplar, oak and maple. In the Adiron- 
dack Mountains as much as ninety per cent of the second growth 
is sometimes made worthless for timber by this wood-rot. The 
decay may extend outward into the sapwood and cause the death 
of the parts above. The characteristics of the sporophores and 
the decay are similar for all kinds of trees affected and are de- 
scribed more fully under poplar diseases, page 305. 



108 MANUAL OF TREE DISEASES 

Uniform White Sapwood-Rot 

Caused by Hydnum septentrionale Fries 

This sapwood-rot is sometimes found in beech and maple. 
The affected wood is white, soft and uniformly rotted. Brown 
zones border the decayed area. V Sometimes single and double 
black lines are irregularly distributed in the white rotted wood. 
Large, heavy, fleshy fruiting-bodies are formed on the side of 
the tree. A thick sheet of mycelium grows over the bark and 
from this project numerous small brackets with the under sur- 
face covered with teeth. The entire structure is white or yel- 
lowish. For further details concerning this sapwood-rot, see 
under maple diseases, page 234. 

White Butt-Rot 

Caused by Fomes applanatus Fries 

The heartwood of the roots and base of the trunk of beech is 
occasionally destroyed by this rot. The decayed wood becomes 
a little lighter in color than the normal wood. It is solid and 
when split longitudinally numerous sinuous whitish tunnels are 
apparent (Fig. 12). The decayed area is bordered by a broad 
discolored zone. The sporophores of the causal fungus are 
woody shelf-like bodies with a brownish or gray, smooth upper 
surface and a white under surface. For further details concern- 
ing this wood-rot, see under poplar diseases, on page 310. 

Parasitized Roots 

Caused by Epiphegus virginiana Barton 

The roots of beech are parasitized by a peculiar flowering 
plant, beech-drop {Eyiyhegus virginiana). This plant belongs 
to the family Orobanchacese, which comprises about one hun- 
dred and fifty species, all of which are parasitic on roots of other 



BEECH DISEASES 



109 



plants. The beech-drop is confined to America and is found 
throughout the range of the beech. The plants grow abun- 
dantly under beech trees in the woods but it is doubtful whether 
much appreciable damage is done to the tree. In this respect 
they may be compared 
with the mycorhizas 
of tree-roots (see page 
82). The beech- 
drop plant is much 
branched, leafless, 
purplish-brown and 
stands from four to 
twelve inches high. 
Small purplish flowers 
are borne on the 
stems in racemes. 1 1 1 
the soil the stem 
ends in a white bulb- 
like or elongate 
rhizome which is cov- 
ered with numerous 
twisted, stiff out- 
growths known as 
grapplers. They serve 
for support and may 
absorb water and 
mineral nutriment. 
All beech-drop plants, 
however, if carefully 
dug, will be found to be attached to small beech roots. The 
tissues of the rhizome of the parasite are fused with those 
of the beech root so completely that at the point of attach- 
ment it cannot be definitely recognized to which plant they 
belong. The beech root is enlarged for some distance each way 




Fig. 12. — Beech wood decayed by Fames 
applanatus. 



no MANUAL OF TREE DISEASES 

from the point of attachment and often the end of the parasi- 
tized root dies, leaving the beech-drop apparently attached to 
the end of a root. Food material for the development of the 
beech-drop is drawn from the beech root, and a large amount of 
starch is formed and stored in the underground rhizome. The 
entire plant dies during the fall and winter and apparently is 
propagated as an annual by over- wintering seed. When de- 
sired, the plants may be eradicated by pulling. This should be 
done before the seeds are formed so as to prevent a crop the next 
season. 

Reference 

Schrenk, Hermann. Parasitism of Epiphegus virginiana. Amer. 
Micros. Soc. Proc. 15:91-128, pis. 1-10. 1894. (Bibliography 
given.) 



CHAPTER XI 
BIRCH DISEASES 

Many species of birch (Betula) occur as forest-trees in the 
United States, especially in the northern parts. The native 
species and imported varieties from Europe and Asia are 
used extensively as ornamentals. 

The leaf-rust is destructive when birch and larch are grown 
close together. The leaf-blister diseases and the several leaf- 
spot diseases (see page 29) are not common and do very little 
damage. Birch is, however, commonly affected by several 
wood-rots, the most important of these being the powdery 
sapwood-rot and common white wood-rot. The other wood- 
rots are not so common and are restricted more or less to certain 
species of birch. 

Leaf-Rust 

Caused by Melampsoridium bctulcr (Sehiim.) Arthur 

The leaves of various species of birch are sometimes affected 
by this rust disease. It has been found in Massachusetts, 
New York, Indiana and Washington and, therefore, probably 
may appear in the northern states wherever birches and the 
alternate larch hosts occur in proximity to one another. The 
leaf-rust is not known to cause any great damage. 

Symptoms. 

Small, round, reddish-yellow pustules appear on the under 
sides of the leaves in the summer. Later in the season a 
second kind of pustule appears on the same leaves. These are 

111 



112 AIANUAL OF TREE DISEASES 

waxy-yellow and finally become brown and almost black. They 
may be abundant and thickly cover the under side of the leaves. 

Cause. 

The rust of birch leaves is caused by Melampsoridium hetulce. 
This fungus occurs also in Europe, where it is known that the 
basidiospores produced from the over-wintering teliospores on 
the birch leaves cause the infection of the young needles of 
larch and produce a blister-rust. The stage on larch has been 
found rarely in this country but very probably exists more 
generally and has been confused with the other rusts of larch 
(see page 212). 

Yellow Leaf-Blister 

Caused by Magnusiella flava (Farlow) Sadebeek 

This leaf-blister disease occurs on white and paper birch in 
northeastern United States. Small light yellow blisters are 
formed on the leaves. The mycelium of the pathogene enters 
the tissue of the leaf and causes a stimulus which results in an 
increase in number and size of the cells. The increased size 
of the affected tissue results in the bulging blisters in the 
leaf. The fungus produces asci containing ascospores on the 
surface of the blisters. 

For the control of this disease, the same methods used for 
peach leaf-curl should give equally good results (Hesler, L. K., 
and Whetzel, H. H., Manual of fruit diseases, p. 277). 

Red Leaf-Blister 

Caused by Exoascus bacteriospernius (Johanson) Sadebeek and Ta- 
phrina carnea Johanson 

Two species of the leaf-blister fungi are found on Behda 
nana. The first mentioned has also been found on Betida 
glandidosa. Although these pathogenes have been described 



BIRCH DISEASES 113 

only briefly from a few collections in northeastern United States, 
Canada and Greenland, they may be more generally distrib- 
uted and common on other species of birch. The lesions 
are confined to the leaves and consist of large reddish brown 
blistered areas, which may cause the leaf to curl. The mycelium 
is confined to the space which it makes for itself between the 
cuticle and the epidermal cells. Due to the parasitic activities 
of these fungi, the tissues of the leaf are stimulated to an in- 
crease both in number and size of the cells. This results in the 
bulging and curling of the leaf between the more rigid veins. 

For the control of these diseases, the same methods that are 
used for peach leaf-curl should give results (Hesler, L. R., and 
Whetzel, H. H., JManual of fruit diseases, p. 277). 

Powdery Sapwood-Rot 

Caused by Polyporus betulinus Fries 

Many species of birch are subject to this sapwood-rot through- 
out the northern hemisphere. Yellow, white and paper birch 
are commonly affected in the United States. Although the 
fungus causing this rot is very common on injured and dead 
birch trees, its importance in causing serious damage to healthy 
trees is questioned. The fungus does not enter through branch 
wounds and other injuries where heartwood is exposed and, 
therefore, never causes a heartwood-rot of the living tree. This 
rot is similar to the yellowish sapwood-rot caused by Fomes 
fomentarins. In the case of both of these fungi, badly injured 
or weakened trees are attacked and the sapwood is the first 
part of the trunk decayed. Later, the fungi extend their 
activities into the heartwood and the entire woody cylinder 
of the trunk is destroyed. These wood-rots are nevertheless 
important in the forest since the timber value of the species 
they affect rapidly deterijrates as soon as the trees become 
mature or injured. 



114 



MANUAL OF TREE DISEASES 



Symptoins. 

The decayed wood is yellowish and cracks radially and tangen- 
tially. The rot is uniform and in the final stages it is very 
light in weight and easily crushed to a powder. 

The sporophores of the causal fungus are very common on 
birch. They are corky annual bodies and are quickly destroyed 
by insects. From the point of attachment to the trunk, they 




Fig. 13. — • Fruitiug-budy of Polyporus hetulinus. 

hang as bell-shaped bodies varying from three to ten or more 
inches across. The outer surface of the sporophore is smooth 
and light to dark mottled gray in color (Fig. 13). The margin 
is incurved and projects below the under surface. The lower 
surface is white or yellowish and roughened by ragged projec- 
tions. The pores are small and the entire layer of tubes 
separates easily from the fruiting-body. 



BIRCH DISEASES 115 



Caiise. 



The powdery; sapwood-rot of birch is caused by Polyponis 
hetulinus. The spores borne in the tubes on the under side 
of the sporophore cause infection in wounds where the sapwood 
is exposed. For a fuller discussion of the life history and control 
of wood-rot fungi, see page 64. 

References 

Schrenk, Hermann von, and Spaulding, P. Decay caused by Poly- 

porus betulinus. In Diseases of deciduous forest trees. U. S. 

Dept. Agr. Bur. PI. Ind. Bui. 149 : 51-52, pi. 9. 1909. 
Mayr, H. Zwei Parasiten der Birke, Polyporus betulinus, Bull., 

and Polyporus laevigatus. Fries. Bot. Centralbl. 19 : 22-29, 51- 

57, pi. 1-2. 1884. 

Yellowish Sapwood-Rot 

Caused by Fomcs fomcntarius Fries 

Yellow birch and beech are commonly affected by this sap- 
wood-rot. Other kinds of deciduous trees are sometimes 
attacked. The sporophores are perennial, light or dark gray 
above, smooth and hoof-shaped with a concave, brown, velvety 
tube-layer. The sapwood is decayed and only an easily 
crumbled mass of fibers is left. A more complete description 
of the symptoms of this wood-rot is given under beech 
diseases, page 105. 

Common White Wood-Rot 

Caused by Fames igniarius Fries 

The common and destructive white wood-rot of poplar, 
beech, oak, maple and other deciduous trees affects the yellow 
and paper birch. Although not as prevalent on birch as on 
manj^ other kinds of trees, it is often found, especially when 
the birches are growing in mixture with the more susceptible 



116 MANUAL OF TREE DISEASES 

host species. The characteristics of the rot and the sporophores 
of the causal fungus are described under poplar diseases, page 
305. The hoof-shaped type of sporophore is more common on 
birch. The sapwood of birch is invaded and the trees die. For 
a general discussion of the life history, dissemination of the . 
spores, mode of infection and control of the wood-rotting fungi, 
see page 64. 

Brown Heartwood-Rot 

Caused by Fomes fulvus Fries 

This heartwood-rot has been found common in river birch 
in Missouri and Arkansas. Other trees are affected by the 
same rot, especially species of Prunus. It is common also in 
fruit-trees of the genus Prunus and in the olive in Europe. 
But little information is available on the rot as it occurs in this 
country. The decayed wood is brown for several feet upward 
and downward from the point where the sporophores are 
formed. In the final stages of the decay the rotted wood 
crumbles easily. Plate-like sheets of mycelium which are 
common in the brown checked wood-rot are lacking in the 
case of this disease. 

The sporophores are formed at wounds. They are perennial, 
hard, woody and more or less hoof-shaped. The tops of the 
older sporophores are smooth and very hard. Fine concentric 
fissures are present but the top does not become roughened. 
The lower surface is reddish brown and covered with minute 
pores. 

For the general life history and control of wood-rotting 
fungi, see page 64. 

Reference 

Schrenk, Hermann von, and Spaulding, P. Red heart-rot of birch 
caused by Fomes fulvus. In Diseases of deciduous forest trees. 
U. S. Dept. Agr. Bur. PI. Ind. Bui. 149 : 47. 1909. 



BIRCH DISEASES 117 

White Butt-Rot 

Caused by Fomes applanatus Fries 

The heartwood of the base of the trunk and the roots of birch 
is sometimes destroyed by this rot. The decayed wood is 
marked by numerous sinuous, white-stuffed tunnels which run 
in the horizontal direction (see Fig. 12, page 109). The sporo- 
phores of the causal fungus are woody, shelf-like bodies with a 
brownish, smooth upper surface and a white under surface. 
This heartwood-rot is more fully described under poplar diseases, 
on page 310. 



CHAPTER XII 
BUCKEYE DISEASES 

The four species of buckeye or ^Esculus native in the United 
States are not important forest-trees. The Ohio and yehow 
buckeye grow to be large trees in the river-bottom lands in 
the central and southern states. A closely related European 
species, the horse-chestnut, is extensively used as an orna- 
mental. 

Leaf-blotch is the most destructive disease affecting buckeye 
and horse-chestnut. This disease occurs every year through- 
out the range of the Ohio and yellow buckeye. The horse- 
chestnut is often severely affected and defoliated in the north- 
eastern states. A powdery mildew is also common on these 
trees. The California buckeye is subject to a leaf-blight and 
witches'-broom disease. The wood and roots of the buckeye 
are rarely diseased. 

Leaf-Blotch 

Caused by Guignardia cesculi (Peck) Stewart 

Throughout central, southern and eastern United States, 
Ohio and yellow buckeye and the horse-chestnut are commonly 
affected by this leaf-blotch. The disease is also known in 
southern Europe. It is probable that the disease is present to 
some extent on the other species of buckeye. A large percentage 
of the foliage of horse-chestnut trees in parks and along streets 
is affected every year. In the nursery this disease interferes 
seriously with the growing of horse-chestnut stock. Repeated 

118 



BUCKEYE DISEASES 



119 



in appearance. Later the center 



defoliation results in retarding the growth of the trees and 
making them more susceptible to winter-injury. 

Symptoms. 

The lesions develop on the leaflets and petiole. When 
first evident, the spots are irregular in outline, slightly dis- 
colored and water-soaked 
of the spot becomes red- 
dish brown and is sur- 
rounded by a yellowish 
zone which blends into 
the green of the healthy 
part of the leaf. Finally, 
the entire affected area 
turns brown and becomes 
dried and brittle (Fig. 14). 
The spots may be small 
or may involve large areas 
and cause a curling of 
the leaflet. Small black 
specks, the fruiting-bodies 
of the pathogene, develop 
either in the lighter colored 
center of the brown blotch 
or may be found distrib- 
uted sparingly over the 
entire dead area. Small 
reddish brown lesions are 
also sometimes formed on 
the petioles. 




Fig. 14. — Leaf-blotch of horse-chestnut. 



Cause. 



The leaf-blotch of horse-chestnut and buckeye is caused 
by the fungus Guignardia ocsculi. Fruiting-bodies containing 



120 MANUAL OF TREE DISEASES 

ascospores are formed in the dead leaves after they fall to the 
ground. These spores mature at about the time the new leaves 
appear in the spring and are disseminated by the wind and 
spattering drops of rain. The lower leaves of young trees and 
sometimes of older ones are the first to show infections in the 
spring, because they are closer to the source of spore-production. 
The first lesions soon develop the other type of fruiting-bodies 
on the dead areas mentioned above. These appear as minute 
black dots. In this stage the fungus is known as Phyllostida 
sphcBwpsoidea. The spores are extruded from the fruiting- 
body and are mainly distributed to healthy foliage by wind and 
rain. By repeated generations of this kind of spores, all the 
leaves on a tree may become infected in a short time. Con- 
tinued or periodically rainy seasons are especially favorable for 
an epiphytotic, since moisture conditions necessary for germina- 
tion are furnished for each new crop of spores. At such times 
the foliage from a distance appears as if scorched by fire and 
considerable defoliation may result. 

Control of leaf-blotch. 

In the nursery it has proved beneficial, in preventing to some 
extent the amount of primary infection, to plow under or rake 
together and burn all dead leaves around the trees. This 
practice can be applied to shade-trees and thus eliminate to a 
large degree the source of early infections. Even when such 
measures are taken, a slight amount of infection may result 
from bits of leaves left on the ground or from early infections on 
trees in the vicinity. It is, therefore, necessary to supplement 
these measures by coating the leaves with some efficient 
fungicide at the time weather conditions and the development 
of the leaves are conducive to infection. Spraying with lime-sul- 
fur (1-50) or bordeaux mixture (5—5-50) will prevent infection. 
The foliage is so dense, however, that thorough spraying cannot 
be done without drenching the foliage. This may lead to 



BUCKEYE DISEASES 121 

unsatisfactory results for two reasons : spray mixtures do not 
act as efficiently if the foliage is drenched, and lime-sulfur 
may cause burning. Dusting nursery trees with a mixture of 
finely ground sulfur and powdered arsenate of lead, in the pro- 
portion of ninety parts of sulfur to ten of lead powder, has 
proved effective in controlling this disease. It may, therefore, 
be assumed that dusting shade and ornamental trees will be 
equally effective. For further directions on spraying and 
dusting for the control of leaf-diseases, see page 357. 

References 

Stewart, V. B. The leaf blotch of horse-chestnut. Cornell Univ. 
Agr. Exp. Sta. Bui. 371 : 411-419, pi. 10, figs. 85-92. 1916. 

Stewart, V. B. The leaf blotch disease of horse-chestnut. Phyto- 
pathology 6 : 5-19, pis. 2-4, fig. 1. 1916. 

Powdery Mildew 

Caused by Uncinula flexuosa Peck 

The leaves of the buckeye and horse-chestnut are affected 
by a powdery mildew, in eastern, southern and central United 
States. The powdery white mycelium usually occurs only on 
the under surface of the leaf in diffused spots. The black 
fruiting-bodies of the fungus are just visible to the unaided eye 
and are found scattered over the mildewed areas late in the 
summer. For a discussion of the general life history and methods 
of control of powdery mildew fungi, see page 37. 

Curled Leaf-Blight and Witches'-Broom 

Caused by Exoascus cesculi (Ell. and Ev.) Patterson 

This disease is described on the California buckeye. It 
occurs in several localities in California. The most noticeable 
symptom is the production of many large witches '-brooms. 
The leaves which are borne on the twigs composing the broom 



122 MANUAL OF TREE DISEASES 

are killed before they mature and appear as frost-injured. 
The mycelium is perennial in the twigs. The leaves of the 
normal branches also become spotted and curled. Small 
yellowish blisters are formed which later turn to a dull red. 
The fungus causing this disease is a close relative of the leaf- 
blister fungus on oak (see page 239) . The disease on the buckeye 
does not cause very much damage to the trees, since the leaves 
naturally remain on the tree only from April to early summer. 

Reference 

Harkness, H. W. The curled leaf {Ascomyces deformans). Zoe 1 : 
87-88. 1890. 

White Sapwood-Rot 

Caused by Collybia velutipes Curtis 

The sapwood of horse-chestnut is sometimes destroyed by 
this toadstool. The wood becomes whitish and soft. The 
spores of the fungus find entrance through wounds in the bark. 
The fruiting-bodies of the causal fungus are toadstools with 
yellow or brownish tops and gills. The bases of the stalks are 
covered wdth a brown or black velvety growth of hairs. A 
fuller discussion of this disease will be found under basswood 
diseases, on page 103. 



CHAPTER XIII 



BUTTERNUT DISEASES 



The butternut (Juglans cinerea) throughout its range in 
eastern and central United States is subject to a few diseases 
only. The most important of 
these is the leaf-spot, which 
also affects walnut and hickory. 
This disease often causes a part 
or all of the leaves to fall from 
the tree in midsummer. Oc- 
casionally the brown checked 
and common white 
are found in butter- 



wood-rot 
wood-rot 
nut. 



Leaf-Spot 



Caused by Marssonia juglandis 
(Lib.) P. Magnus 

This is the common leaf- 
spot of butternut and walnut. 
Irregular dark brown spots ap- 
pear on the leaflets in early 
summer. When infection is 
abundant, a large amount of 
the leaf-tissue is killed and the 
leaves fall from the tree. The illustration 
leaflet affected by this disease (Fig. 15). 

The parasitic fungus causing the spots forms inconspicuous 

123 




Fig. 15. 



Leaf-spot of butternut. 

shows a single 



124 MANUAL OF TREE DISEASES 

fruiting-structures on the under sides of the dead areas. Spores 
from these structures are produced in abundance during wet 
weather and are disseminated by rain. After the leaves fall, 
perithecia are formed and from these ascospores are available 
in the spring for primary infection. The name applied to the 
perithecial stage is Gnomonia leptostyla (Fries) Ces. and De 
Not. For a further discussion of leaf-spots and their control, 
see page 27. 

Common White Wood-Rot 

Caused by Fomes igniarius Fries 

The butternut is sometimes affected by the common white 
wood-rot, which occurs in many kinds of deciduous trees, 
especially poplar, beech, oak and maple. The sporophores 
of the fungus and the characteristics of the rot are similar for 
all the kinds of trees affected and are described under poplar 
diseases, page 305. 

Brown Checked Wood-Rot 

Caused by Polyporus sulphurous Fries 

Butternut is occasionally affected by the brown checked 
wood-rot, caused by the sulfur fungus. Many other kinds 
of trees are affected by the same disease. The sulfur-yellow, 
annual fruiting-bodies of the fungus together with the brown 
powdery character of the rotted wood make it easy to identify 
this disease. The tops of trees and large limbs may be killed 
by the invasion of the sapwood and bark. A more complete 
discussion of this wood-rot will be found under oak diseases, 
page 247. 



CHAPTER XIV 

CATALPA DISEASES 

The two species of catalpa grow naturally in southeastern 
and central United States. Both species are used as orna- 
mentals. A few leaf-spot diseases cause some damage to 
catalpa according to the locality and the season (see page 30). 
Otherwise the tree is not subject to serious diseases, except 
in plantations where the yellow wood-rot is destructive. The 
predisposing of the catalpa to this wood-rot, by planting the 
trees closely, illustrates the importance of branch wounds 
as infection courts for the heartwood-rotting fungi. The 
rapidity with which this rot progresses in the living tree com- 
pared with the well-known durability of catalpa timber points 
to the existence of some condition within the tree which favors 
the development of the causal fungus. 

Yellowish Wood-Rot 

Caused by Polysiictus versicolor Fries 

This destructive heartwood-rot of the hardy catalpa may 
be found wherever the trees grow. The disease is not common 
in trees growing in the open. In close stands, however, the 
limbs are killed by shading and after they break away, holes 
are left which soon become infected by the spores of the fungus 
causing this rot. The causal fungus is a very common sapro- 
phyte, which grows everywhere on the wood of deciduous 
trees. It may often occur as a semi-parasite in the bark and 

125 



126 MANUAL OF TREE DISEASES 

sapwood of deciduous trees when they have been severely 
injured. Otherwise the catalpa is the only tree in which this 
fungus is known to cause a distinctive heartwood decay. 

Symytoms. 

The affected trees may be recognized by the holes in the 
trunk where the old branch stubs have rotted. Insects and 
birds remove the decayed wood and use the hollowed-out areas 
in the trunk for habitations. In cross-sections of the trunk, 
the first indications of the decay show as pale colored areas. 
The spring-wood of the annual rings becomes reddish with small 
whitish areas. Later both the spring- and summer-wood of 
the annual rings are similarly affected. The decayed wood then 
becomes straw-yellow and is very soft and brittle. The de- 
cayed area enlarges rapidly and eventually the sapwood may 
be invaded. The decay may extend into the branches and 
roots. Coppice is usually affected if the wood of the stump is 
decayed. 

The fruiting-bodies of the causal fungus are formed where 
the bark is dead or on the affected wood when it is cut from 
the tree. They are thin, tough shelving structures, hairy on 
top and marked with variable yellowish and brown shiny zones. 
The under surface is yellowish or white and covered with small 
pores. The fruiting-structures are annual bodies but they 
persist through the winter and may revive and shed spores in 
the spring. 

Cause. 

The yellowish soft wood-rot of hardy catalpa is caused by 
the fungus Polystictus versicolor. The spores from the tubes 
on the under surface of the fruiting-bodies are wind-borne 
and cause infection when they lodge in branch wounds. When 
the trees are planted close together, the lower shaded branches 
die and remain attached to the tree for some time. When 



CAT ALP A DISEASES 127 

they are broken off, a hole is left in the trunk which serves as 
an excellent infection court. The mycelium progresses rapidly 
in the wood. For further details concerning the life history 
and control of the wood-rotting fungi, see page 64. 

Control. 

As a means of preventing loss from this rot in plantations, 
it is advised that the lower limbs should be pruned oft' and the 
wounds treated with a dressing. Directions for these opera- 
tions will be found on page 345. 

References 

Sehrenk, Hermann von. II Diseases of the hardy catalpa. In The 

hardy catalpa. U. S. Dept. Agr. Bur. Forestry Bui. 37 : 49-58, 

pis. 23-30, figs. 1-2. 1902. 
Stevens, Neil E. Polystietus versicolor as a wound parasite of 

catalpa. Mycologia 4 : 26.3-270, pis. 74-75. 1912. 
Stevens, Neil E. Wood rots of the hardy catalpa. Phytopathology 

2: 114-119, pi. 10. 1912. 

Brown Butt-Rot 

Caused by Polyporus {Porta) catalpce Sehrenk 

The heartwood and sapwood of the base of the hardy catalpa 
is sometimes affected by this brownish wood-rot. The wood 
becomes reddish brown and crumbly. It cracks along the 
annual rings and at times across them, leaving spaces which 
are filled by felts of mycelium. The fruiting-bodies of the 
causal fungus are described as thin sheets of mycelium which 
lie closely appressed to the diseased wood. The surface is 
covered with small pores which are the openings of perpen- 
dicular tubes in which the spores are borne. The fruiting- 
structures are at first whitish, but later become yellowish and 
brown. This fungus enters the tree through the branch wounds 
in the same way as described under the yellowish wood-rot 



128 MANUAL OF TREE DISEASES 

(see page 125). The control is the same for both of these dis- 
eases. 

Reference 

Schrenk, Hermann von. II Diseases of the hardy catalpa. In The 
hardy catalpa. U. S. Dept. Ag:\ Bur. Forestry Bui. 37 : 49-58, 
pis. 23-30, figs. 1-2. 1902. 



CHAPTER XV 
CEDAR DISEASES 

The white cedar of the Atlantic Coast and incense cedar of 
the Pacific Coast are affected by several destructive diseases. 
These two trees belong to different genera (Chamsecyparis 
and Libocedrus). The diseases affecting the white cedar do 
not occur on the incense cedar and vice versa. They are dis- 
cussed together in this chapter merely for the convenience of 
grouping them under the name common to both. 

The two rust diseases (witches'-broom and branch-swellings) 
on the white cedar cause serious deformation of the trees and 
even death when they occur. The incense cedar is also af- 
fected by a rust-fungus which causes witches'-brooms. The in- 
cense cedar is subject to a destructive heart wood-rot, which 
is similar in appearance to the pecky heartwood-rot of bald 
cypress. The brown felt-blight of incense cedar is important 
at high altitudes. 

Eastern Leaf-Rust 

Caused by Gymnosporanguim fraternum Kern 

The white cedar is sometimes affected by this leaf-rust, 
along the Atlantic Coast from Massachusetts to New Jersey. 
No damage is done to the trees. The symptoms are confined 
to the spore-masses of the pathogene which break through the 
epidermis of the affected leaves. These spore-masses appear 
in the spring and are small brown cushion-shaped pustules 
about an eighth of an inch in diameter. The life history of 
the causal pathogene is completed on the leaves of chokeberry 
L 129 



130 MANUAL OF TREE DISEASES 

(Pyrus). The teliospores borne on the brown cushions ger- 
minate and the basidiospores which are formed in this process 
are blown away and cause the infection of the chokeberry 
leaves, ^ciospores produced on this host plant then cause 
infection of the cedar leaves later in the season if they 
chance to lodge on them. A more detailed explanation of 
the life history and control of the rust-fungi belonging to the 
same genus as this pathogene will be found under juniper dis- 
eases, on page 192. 

Western Leaf-Rust 

Caused by Gymnosporangium nootkatensis (Trelease) Arthur 

Along the Pacific Coast in the Northwest, the yellow cedar 
is affected by this leaf-rust. The symptoms are similar to the 
eastern leaf-rust described above. The life history of the causal 
pathogene is completed on the leaves of species of apple and 
mountain ash. For a more detailed description of the habits 
and control of the rust-fungi of this genus, see under eastern 
leaf-rust, above, and juniper diseases, on page 192. The life 
history of this rust-fungus differs, however, from all of the 
other species of the genus Gymnosporangium, in that uredinio- 
spores are formed on the cedar leaves. The teliospore-cushions 
have not been found but undoubtedly occur on the cedar 
leaves associated with the urediniospores. 

Brown Felt-Blight 

Caused by Herpotrichia nigra Hartig 

Incense cedar is one of the many conifers subject to this 
disease in the Northwest. The leaves and twigs are covered 
with a dark brown mat of mycelium (Fig. 16). The mycelium 
also enters the leaf-tissues. Young trees and the lower branches 
of older ones are killed and under conditions favorable for the 
development of the causal fungus, the trees appear as scorched 



CEDAR DISEASES 



131 



by a ground fire. The same disease affects similarly spruce, 
fir, juniper, arbor-vitse and hemlock. It is described under 
spruce diseases, on page 317. 




Fig. 16. — Brown felt-blight on incenso cedar. 



E.^STERN WiTCHES'-BrOOM 
Caused by Gymnosporangium myricatum (Seliw.) Fromme 

Witches '-brooms are found on white cedar along the At- 
lantic Coast from Massachusetts to Delaware and in northern 
Florida and southern x\labama. The witches'-broom and 
branch-swelling diseases, both caused by similar rust-fungi, 



132 MANUAL OF TREE DISEASES 

are the most Important diseases of white cedar. As in the case 
of the other rust-fungi of cedar and juniper, an alternate host 
is necessary for the completion of the life history of the fungus. 
The witches '-brooms are never formed unless bay berry, sweet- 
fern or wax myrtle shrubs (Myrica) are in close proximity to 
the cedars. 

Symptmns. 

The infected branches of the cedar become slightly swollen 
and produce many short laterals which form a compact broom- 
like growth. In the early spring, orange spore-horns about an 
eighth or a quarter of an inch long project from the bark of 
the distorted branches. 

Cause. 

The witches '-brooms of white cedar are caused by the rust- 
fungus, Gymnosporanglum myricatum. The life history of 
this fungus is similar to that of the other cedar and juniper 
rusts except that the alternate stage is developed on species 
of Myrica. With this exception the life history described on 
page 192 will apply in general to this species. 

Control. 

Since this rust-fungus requires the presence of both the 
white cedar and species of Myrica in close proximity in order 
to carry out its life history, a simple means of protecting the 
cedars is afforded by destroying the bayberry, sweet-fern or 
wax myrtle shrubs. If these plants can be eliminated for a 
distance of several hundred feet or a mile from the white cedars, 
no further exchange of spores will be likely and the cedars will 
be safe from infection. 

References 

Harshberger, J. W. Two fungous diseases of the white cedar. Proc. 

Acad. Nat. Sci. Phila. 1902 : 461-504. 1902. 
Fromme, F. D. A new Gymnosporangial connection. Mycologia 

6 : 226-230. 1914. 



CEDAR DISEASES 133 

Western Twig-Blight and Witches'-Broom 

Caused by Gyninosporangiutn Blasdaleanum (Diet, and Holw.) Kern 

The incense cedar is attacked by this rust disease and con- 
siderable damage is caused in some regions. The other trees 
attacked by the same rust, in the other stage of its Hfe history, 
are cultivated apple, pear, quince, mountain ash and wild 
species of apple, haw and service-berry. It is most destruc- 
tive on the cultivated pear. The relation between the stages 
of this fungus on the two types of hosts, one the incense cedar 
and the other the plants of the apple family, is explained on 
page 192, where the life history of these rusts is discussed. 

Symptoms. 

Two different effects are produced by this rust. When the 
smaller twigs are infected, the first symptoms in early spring 
are the small reddish brown spore-cushions which appear on 
the surface of the scale-like leaves. During rainy weather 
these cushions gelatinize and coalesce, forming yellowish masses 
over the leaves. The leaves of the infected twig then turn 
yellow and the twig dies. 

When larger branches are infected, dense clusters of upright 
branches are produced. The fungus fruits in the manner 
described above on the younger twigs of the brooms and the 
twigs are killed. Most of the damage caused by this rust on 
the incense cedar is due to the development of the witches'- 
brooms which at times seriously deform the tree. 

Cause. 

The twig-blight and witches'-broom of incense cedar are 
caused by. the rust-fungus, Gymnosyorangium Blasdaleanum. 
The teliospores formed on the spore-cushions on the cedar ger- 
minate and produce basidiospores, which when blown to the 



134 MANUAL OF TREE DISEASES 

apple host cause infection of the leaves. The seciospores formed 
sometime later infect the cedar leaves in the summer and au- 
tumn. The fungus over-winters as mycelium in the cedar 
leaves. Further details concerning the life history of rusts of 
this type will be found under juniper diseases, on page 192. 

References 

Jackson, H. S. A Pacific Coast rust attacking pear, quince, etc. 

Second Biennial Crop Pest and Horticultural Report (Oregon 

Agr. Exp. Sta.) 1913-1914 : 204-212. 1915. 
Jackson, H. S. A new pomaceous rust of economic importance, 

Gymnosporangium Blasdaleanum. Phytopathology 4 : 261-269, 

pis. 12-13. 1914. 

Branch-Swelling 

Caused by Gymnos'porangium botryapites (Sehw.) Kern 

The white cedar on the Atlantic Coast from Massachusetts 
to New Jersey and Pennsylvania and in southern Alabama 
is often affected by this disease. The branch-swelling and 
witches'-broom diseases of white cedar are the most serious 
to this tree. Because, however, of the peculiar life history 
of the rust-fungi which cause them, they are not generally 
prevalent. The spores formed on the cedar branch-swellings 
cause the infection of the leaves of the service-berry and an- 
other type of spores formed on these leaves in turn causes 
infection of the branches of the white cedar. Thus it is seen 
that this fungus cannot exist unless the service-berry is in close 
proximity to the cedars. 

Symptoms. 

The infected branches become swollen to two or three times 
the normal size. The swellings are spindle-shaped and may be 
several inches long. In the spring, brown pustules about an 
eighth by a quarter of an inch burst through the bark of the 



CEDAR DISEASES 135 

swellings. These pustules become gelatinous and sometimes 
may become confluent. 

Cause. 

The branch-swellings of white cedar are caused by the rust- 
fungus, Gijmnosporangium hoiryapitcs. The teliospores pro- 
duced on the brown pustules on the cedar bark germinate and 
form basidiospores which are innocuous to the cedar and can 
infect onh^ the leaves of the common service-berry. Here, 
after a few weeks' growth, seciospores are formed which, if 
they find their way to the white cedar, cause the infection of 
the branches and the swellings result after a year or two. For 
further details concerning the life history of this type of rust, 
see page 192. 

Control. 

Since the fungus can only exist in a region where the white 
cedar and service-berry stand within a relatively short distance 
of each other, the eradication of the service-berry serves as a 
simple method of control. A separation of these two kinds of 
trees by a few hundred feet may prove effective, although for 
similar rusts of the juniper, a mile has been found to be a more 
desirable distance. 

Reference 

Harshberger, J. W. Two fungous diseases of the white cedar. Proc. 
Acad. Nat. Sci. Phila. 1902 : 461-504. 1902. 

Pecky Heartwood-Rot 

Caused by Polyporus amarus Hedgcock 

The heartwood-rot of incense cedar, known as pin-rot, pecki- 
ness, dry-rot or pin-disease, does great damage to this tree in 
California and Oregon. All of the trees in a given area are 
sometimes found to be affected, the middle portion of the 



136 MANUAL OF TREE DISEASES 

trunk being most often decayed. Trees less than one or two 
feet in diameter are not usually attacked. 

Symptoms. 

The appearance of the affected wood is very similar to the 
pecky heartwood-rot of cypress (see page 97). Long lens- 
shaped pockets are formed parallel with the grain of the wood. 
The pockets are filled with a brittle brown mass of decayed 
wood. The surface of the pockets is smooth and the wood 
immediately surrounding is sound. The first evidence of 
the decay is the darkened color of certain areas varying from 
one to ten inches long and from one-fourth to one inch wide. 
The affected wood in these areas is quickly reduced to a brown 
charcoal-like mass. The pockets vary in arrangement and 
number much as in the pecky heartwood-rot of cypress, and 
a similar brown humus-like powder is found in the cells around 
the margin. The sporophores of the causal fungus are hoof- or 
bell-shaped bodies appearing at knot-holes in affected trees. 
They are large bodies, several inches across, soft and spongy 
when young and later becoming tough and chalky. The upper 
surface is at -first light brown in color but soon becomes darker 
brown, especially around the margin. The under surface is 
yellow or yellow-green and turns brown with age. The pores 
are small. The fruiting-bodies are soon destroyed by insects. 

Cause. 

The pecky heartwood-rot of incense cedar has been shown 
to be associated with the fruiting-bodies of the polypore, named 
Polyporus amarus. This fungus was previously called Poly- 
porus Lihocedrus von Schrenk. The spores borne in the tubes 
on the under surface of the fruiting-body cause infection of the 
heartwood of the cedar at branch wounds. The sapwood is 
not affected. For the details of the general life history and 
control of wood-rots, see page G4. 



CEDAR DISEASES 137 

The pecky rots of incense cedar and cypress are, as pointed 
out above, very similar in many respects but are now known 
to be caused by different species of fungi. 

References 

Schrenk, Hermann von. A disease of Taxodium distichum known as 
peckiness, also a similar disease of Libocedrus decurrens known 
as pin-rot. Missouri Bot. Gard. Rept. 11 : 23-77, pis. 1-6. 1900. 

Hedgcoek, G. G. A new polypore on incense cedar. Mycologia 2 : 
155-156. 1910. 



CHAPTER XVI 
CHESTNUT DISEASES 

The chestnut was until recently one of the important forest- 
trees of New York, Connecticut, Pennsylvania and the Alle- 
ghany Mountain region southward to' Alabama. Besides its 
commercial value as timber, the chestnut was important also 
in its natural range as a much-favored ornamental. As an 
orchard-tree, the varieties of the American and foreign species 
are of relatively less importance. 

Fifteen years ago the chestnut was not subject to any very 
destructive diseases. With the appearance of the Endothia 
canker or blight, however, the very existence of the species 
seemed threatened. During the first ten years of the spread 
of the fungus causing this disease, all the chestnut trees over 
hundreds of square miles were killed. The disease is now 
prevalent over practically the entire range of the chestnut 
and apparently only a negligible number will escape destruction. 
It is unusual for a parasite to be so adapted that all the individuals 
are equally susceptible to its attack. Many limiting factors 
of resistance, temperature, moisture, seasonal conditions, dis- 
seminating agents and the like serve to hold parasitic fungi 
in check. The fungus causing the canker, however, is the 
extreme example of an introduced parasite which is perfectly 
adapted to the host and the environmental conditions of eastern 
United States. 

With the passing of the chestnut, it is scarcely necessary to 
consider other less important diseases of this tree. Several 
leaf-spot diseases are common on chestnut. In the North 

138 



CHESTNUT DISEASES 139 

the one caused by Septoria ochroleuca is important. The large 
leaf-spot is common in the South. Powdery mildews are 
also common on chestnut leaves. The wood of the trunk is 
decayed by several fungi and the shoe-string root-rot is very 
destructive to chestnut (see page 78). 

Large Leaf-Spot 

Caused by Monochatia Desmazierii Saec. 

Chestnut leaves are commonly affected by leaf-spot diseases. 
The one here designated as the large leaf-spot is known to occur 
in the southern Appalachian region in Virginia, North Carolina 
and Georgia. It is often abundant, and causes some damage 
by decreasing the functioning leaf-surface. Red oak leaves are 
affected by the same disease. 

Symptoms. 

The symptoms are similar on the chestnut and red oak. 
Small circular spots appear which are a quarter to one-half 
inch in diameter, with a pale center and darker surrounding 
zones, varying in color from yellow and gray to red-brown. 
These spots enlarge rapidly and sometimes extend entirely 
across the width of the leaf. Two or three such spots cause 
the death of most of the leaf-tissue. The bands of colors as 
described above are present in the older and larger spots. On 
the under side of the leaf there is less evidence of the colored 
zones and superficial mycelium of the fungus at the margin of 
the spot causes a mildewed appearance. Early in the develop- 
ment of the spots, numerous densely crowded black dots appear 
on the dead leaf-tissue. 

Cause. 

Large leaf-spot of chestnut and red oak is caused by the 
conidial stage of a fungus known as Monochoetia Desmazierii. 



140 MANUAL OF TREE DISEASES 

But little is known of the life history of this parasite. The 
spores produced in the black dot-like fruiting-bodies on the 
spots have been proved to infect other healthy chestnut leaves. 
In this way the fungus is probably disseminated by the rain 
washing and spattering the spores. A perithecial stage of the 
fungus is probably developed in the dead leaves on the ground 
from which primary infection may be brought about in the 
spring. This point is, however, undetermined. 

Control. 

Apparently no attempts have been made to control this 
disease. General suggestions for the control of leaf-spot dis- 
eases are given on page 33 and may be of some application to 

this disease. 

Reference 

Graves, A. H. The large leaf spot of chestnut and oak. Mycologia 
4 : 170-174, pi. 69, fig. 1. 1912. 

Twig-Blight 

Caused by Sphceropsis malorum Berkeley ( = Physalospora cydonice 

Arnaud) 

This twig-blight is more common and destructive on chestnut 
oak. It occurs occasionally on chestnut in central eastern 
United States. Cankers are formed on the small branches 
and twigs. The leaves wilt and turn brown in midsummer. 
A fuller description of this disease and its control will be found 
under oak diseases, on page 244. 

Endothia Canker 

Caused by Endothia parasitica (Murr.) Ander. and Ander. 

All the species of the genus Castanea are susceptible to this 
destructive fungus. The trees included in this group are : 
the common American chestnut, the eastern chinquapin, the 



CHESTNUT DISEASES 141 

European and the Japanese chestnut and the western chin- 
quapin (genus Castanopsis). Pure strains of the Japanese 
varieties are resistant while all the other species are very sus- 
ceptible. From an economic standpoint, the American chest- 
nut is by far the most important species. 

The Endothia canker has also been known by the common 
names, chestnut-blight and chestnut bark-disease. It was 
first noticed in the New York Zoological Park in 1904. Since 
that time it has spread for hundreds of miles, north, west and 
south. It has proved to be the most destructive and rapidly 
spreading tree disease known. The areas which have been 
swept by the epiphytotic so far, are left apparently without a 
single living chestnut tree. After many years of speculation as 
to the past history of this disease, it was discovered in northern 
China in 1913 and later in Japan. It is of slight importance in 
its native home. There is little doubt now that the Japanese 
chestnuts imported into this country brought with them this 
unnoticed disease of the Orient. The increased destructiveness 
of the disease in this country is due to the greater susceptibility 
of the American chestnut. Many examples of epiphytotics due 
to newly imported pathogenes are now a matter of record and 
make the regulation of the interchange of plant products one 
of the important phases of plant disease control. 

Symptoms. 

The tissues of the bark, including the cambium, are invaded 
and killed. The dead areas of bark, or cankers, are especially 
conspicuous on the younger limbs where the normal bark is 
smooth and green. They may be seen at a distance because 
of the reddish color of the dead bark in contrast to the healthy 
green bark. Usually the cankered area is slightly sunken, 
due to the killing and drying of the tissues. On young rapidly 
growing coppice, however, swollen areas (hypertrophy cankers) 
with the bark split open lengthwise are commonly found. Dur- 



142 



MANUAL OF TREE DISEASES 



ing midsummer the cankers enlarge at the rate of about one- 
half inch in diameter each week. The usual shape of the canker 
is ellipsoidal (Fig. 17). The margin of 
the canker is usually regular and some- 
what raised. On smooth bark, the thin 
cork-layer is wrinkled, forming concen- 
tric rings about the central point of 
the canker. As the canker becomes 
larger, the bark splits and after a time 
falls away in shreds, leaving the wood 
bare. 

When the fungus is working in the 
living tissues under the rough bark, there 
are no outward indications of its pres- 
ence until the fruiting-structures are pro- 
duced in crevices of the bark. If the 
bark is peeled from the edge of a canker, 
the tawny mycelial fans are readily seen 
(Fig. 18). The invaded tissues are 
changed to a light brown in contrast to 
the normal light colored healthy tissue 
of the bark. The thick bark is reduced 
to a mass of shreds which are a uniform 
dark brown. The first layers of wood 
under the cankered areas also become 
brown. 

The effects of the disease on the 
general appearance of the tree are most 
noticeable during the summer when the 
trees are in leaf. In localities in which 
the disease is common, large numbers 
of the newly affected branches and twigs 
are girdled by the cankers during the late summer and the 
brown shriveled leaves hang to the limbs. This most striking 




Fig. 17. — Endothia canker 
of chestnut. 



CHESTNUT DISEASES 



143 



symptom is common in July and August. The dead leaves 
remain clinging to the limbs during the winter. If the girdling 
of the limb is completed at a time when the burs are matur- 
ing, these also remain on the tree over winter. In case the 
girdling of the limb takes place in late autumn or early spring, 
after the leaves and burs are shed, the new leaves never attain 
their full size but remain pale green and distorted. This is a 
common symp- 
tom in INIay and 
June. Cankers 
on the trunk, es- 
pecially if at the 
base, cause the 
development of 
clumps of water- 
sprouts or suckers 
below the can- 
kered area. Such 
clumps of suckers 
do not constitute 
infallible signs of 
the Endothia 
canker, however, 
since girdling 
caused by any 

agency will re- Fig. is. — Mycelial fans l at wr.-n the bark and wood. 

suit in such out- 
growths. After a tree has become thoroughly diseased — and 
this may take only three or four years after the first ap- 
pearance in the top of the tree — the brown fruiting-pustules 
of the fungus cover the dead bark of the trunk and branches, 
giving the tree a distinctive red-brown hue. The fungus con- 
tinues to live saprophytically on the dead bark, as long as any 
remains. 




144 MANUAL OF TREE DISEASES 

Cause of Endothia canker. 

The canker of chestnut is caused by the peritheciura-forming 
fungus Endothia parasitica, formerly called Diaporthe parasitica. 
The mycelium may grow parasitically in the bark, cambium 
and sapwood of all parts of the chestnut tree above ground or 
saprophytically on bark, twigs and dead parts of chestnut 
and other trees. In the northern states new cankers may 
originate at any time of the year from March to October. The 
dissemination of the fungus to healthy trees or healthy parts 
of the same tree is accomplished by many different agencies. 
The spores or the mycelium itself may be carried by the wind, 
water, birds, quadrupeds, insects and often by man. The 
spores and mycelium live through the winter uninjured and 
are ready for dissemination in the spring when many primary 
infections are started. The agency most largely concerned in 
the rapid spread of this fungus from tree to tree is the wind, 
while water is important in washing the spores from a canker 
in the top of a tree to other parts of the same tree and to others 
close by. A few of the millions of spores produced on a single 
canker find lodgment on the bark of other chestnut trees after 
a shorter or longer journey from the place where they were 
produced. Bringing the spores into contact with the healthy 
bark is not all that is sufficient, however, for the spores must 
find a wound of some kind to accomplish infection. The 
spores germinate during periods of moist weather and the short 
germ-tubes enter the soft tissue of the bark through the wound. 
If there is no wound in the cork-layer, the germ-tubes of the 
spores are unable to penetrate. An abundant growth of my- 
celium rapidly develops from the germ-tube and in a few days 
thin fan-like plates composed of thousands of threads of my- 
celium, growing side by side, push out into the soft tissues of 
the bark which lie between hard fibrous layers (Fig. 18). The 
cells are killed a little in advance of the mycelium by certain 
poisons which are excreted. Therefore, as these mycelial fans 



CHESTNUT DISEASES 



145 



grow out from the point of infection in all directions, the tissues 
of the bark are killed and soon a rapidly enlarging canker be- 
comes apparent. 

About a month after infection is accomplished, the surface 
of the small canker becomes covered with numerous small 
blisters (Fig. 19). These blisters are produced by balls of 
mycelium formed under the cork-layer. Within these balls 
are formed one of the types of spores (the conidia). During 
moist conditions, following rains, 
long, twisted, yellow tendrils are 
pushed out from the ruptured bark 
over each blister (Fig. 19). The 
tendrils are a mass of the very 
small spores dried into this shape 
after being squeezed through a 
small opening. The next rain or 
dew causes these tendrils to sepa- 
rate into the thousands of spores 
in each and they then may be 
washed or spattered about by the 
water or carried by animate agents. 
Any one of these spores germinat- 
ing where the germ-tube may enter 
wounded bark-tissue may initiate 
a new canker. 

On older and larger cankers, the blisters and yellow tendrils 
of spores are confined to the margin, while nearer the center, 
reddish brown pustules of mycelium are pushed out through 
the bark. They measure when fully developed one-sixteenth 
of an inch or more in diameter and have numerous papillae on 
the upper surface, each with a black dot in the tip (Fig. 20). 
Within the brown pustules, buried below the surface of the 
bark, are formed thirty or more cavities (perithecia) , within 
each of which are produced in great abundance another type 




Fig. 19. — Spore-horns of chest- 
nut canker fungus. 



146 



MANUAL OF TREE DISEASES 



of spore (the ascospores). These spores are confined in small 
delicate sacs, eight spores in each sac or ascus. During rainy 
periods, these sacs swell and a certain number are forced up 

through a tube leading from each 
cavity to the black mouths at the 
tips of the papillae. Once out- 
side, the sacs burst and the eight 
spores in each are shot into the 
air where they are carried away 
by the wind to great distances. 
It is these wind-blown ascospores 
which account fcr the extreme 
rapidity of spread of this fungus 
and make certain the infection of 
all trees in the vicinity. 

The living tissues of the bark 
and the cambium are killed and 
the mycelium enters the first layer 
or two of the sapwood. The 
indirect effect, when these tissues 
are killed entirely around a limb, 
is the withering and dying of the 
parts above. The tree is thus 
killed by the successive girdling 
of the limbs and finally by cankers 
developing on the trunk. 




Fig. 20. — Perithecial stage of 
chestnut canker fungus. 



Control of Endothia canker. 

After the chestnut canker had 
developed into a destructive 
epiphytotic in Connecticut, New York, New Jersey and Penn- 
sylvania, many investigations were begun to determine the 
facts with regard to the disease and especially with a view 
toward its control. A method was proposed of eliminating 



CHESTNUT DISEASES 147 

all diseased trees in spot infections somewhat distant from the 
generally infested areas and the surrounding of the area already 
invaded, by a zone from which all chestnut trees were to be cut 
and removed. Much effort was expended in 1911 and 1912 
to locate and map the regions in which this method would be 
put into effect. Trial areas were located and all diseased trees 
were cut, the timber peeled and the refuse burned. The 
enormous effort involved in carrying out such a plan to control 
the disease seemed far too expensive and the results too prob- 
lematical to warrant their continuance. Pennsylvania, how- 
ever, by the appointment of a special commission, attempted 
to carry out the eradication methods in that state, but discon- 
tinued the work in 1913 after two years' trial. Since that time 
the canker has continued its destruction and is gradually ex- 
tending its range into the northern limits of the chestnut in 
the New England states, western New York and Ohio and into 
the southern Appalachians, threatening the total extinction of 
the tree. 

The attempt to control chestnut canker in individual trees, 
when the expense of surgical methods is warranted, may be 
successful. By the ordinary methods of canker eradication, 
the diseased areas may be removed. Especial care is necessary 
in order completely to remove the fungus. The bark should 
be cut away at least an inch be^^^ond the apparent edge of the 
canker and the wood beneath the area of bark thus removed 
must be chiseled out to a depth of an inch. Coal-tar dressing 
then should be applied to the exposed wood and bark. After 
all the cankers are removed, careful watch must be kept for 
the appearance of new cankers. If the tree is large and has 
rough bark, the chances of discovering all the diseased areas 
in time are small. 

The Japanese varieties are sufficiently resistant, if pure stock 
and not grafted on American roots, to warrant their use as 
orchard-trees. The crossing of the Japanese and Chinese with 



148 MANUAL OF TREE DISEASES 

the American chestnut may yield a resistant variety which 
can be grown with relative immunity to this disease. The 
advertisements of resistant chestnuts at this time, however, 
are misleading, since none has been developed. 

References 

Anderson, P. J., and Rankin, W. H. Endothia canker of- chestnut. 
Cornell Univ. Agr. Exp. Sta. Bui. 347: 531-618, pis. 36-40, 
figs. 77-101. 1914. 

Anderson, P. J., and Babeock, D. C. Field studies on the dissemination 
and growth of the chestnut tree blight fungus. Pennsylvania 
Chestnut Tree Blight Com. Bui. 3 : 1-32. 1913. 

Clinton, G. P. Chestnut bark disease. Connecticut Agr. Exp. 
Sta. Rept. 36 : 359-453, pis. 21-28. 1913. 

Giddings, N. J. The chestnut bark disease. West Virginia Agr. 
Exp. Sta. Bui. 137 : 209-225, figs. 1-12. 1912. 

Heald, F. D. The symptoms of chestnut tree blight and a brief de- 
scription of the blight fungus. Pennsylvania Chestnut Tree 
Blight Com. Bui. 5 : 1-15, pis. 1-16. 1913. 

Metcalf, H., and Collins, J. F. The control of the chestnut bark dis- 
ease. U. S. Dept. Agr. Farmers' Bui. 467 : 1-24, figs. 1-4. 1911. 

Rankin, W. H., Field studies on the Endothia canker of chestnut in 
New York State. Phytopath 4 : 233-260, pi. 11, figs. 1-2. 1914. 

Anonymous. Treatment of ornamental chestnut trees affected with 
the blight disease. Pennsylvania Chestnut Tree Blight Com. Bui. 
2:1-7. 1912. 

Strumella Canker 

Caused by Strumella coryneoidea Sacc. and Winter 

This canker occurs on chestnut but is more destructive on 
various species of oak. On chestnut the sunken cankers are 
distinguishable from the Endothia canker or blight, but in 
general the tree is very similarly affected. The first signs of 
the developing canker on smooth-barked trees appear as yellow- 
ish or brownish slightly raised areas around a branch stub. 
Many black nodules an eighth of an inch in diameter are 
formed on the surface of the affected bark. When the bark 
is peeled from the cankers, sheets of pure white or only 



CHESTNUT DISEASES 149 

slightly tan-colored mycelium are exposed. No indications 
of mycelial fans are found as in the Endothia canker. The 
cankers soon girdle the trunk and the parts above die. Large 
elliptical conspicuous cankers with depressed centers surrounded 
by concentric calluses are also formed on chestnut but not so 
commonly as on the red and black oak. These cankers and 
the fungus causing them are described on page 245. 

Brown Checked Wood-Rot 

Caused by Polyporus sulphureus Fries 

The heartwood and sapwood of chestnut are often decayed 
by the sulfur fungus. The same rot is common in oak, maple, 
walnut, butternut, locust, alder and other trees. The wood 
is reduced to a red-brown, powdery mass which separates into 
cubes. The sporophores are conspicuous, annual, orange and 
sulfur-yellow colored bodies which form at wounds or on the 
bark where the fungus has decayed the sapwood. The tops 
of the trees or large limbs may be killed by the girdling action 
of the mycelium in destroying the sapwood and bark. A fuller 
description of the symptoms and cause of brown checked wood- 
rot which are similar for all the trees affected is given under oak 
diseases, page 247. 

Straw-Colored Heartwood-Rot 

Caused by Polyporus frondosus Fries 

This heartwood-rot may be found in the base of the trunks 
of chestnut. The trees do not become hollow. The advancing 
decay first shows as long, slender, white streaks. Later the 
wood becomes tan- or straw-colored and is held together by 
the less affected medullary-rays. The sporophores of the causal 
fungus arise from the ground around the affected tree. They 
are large, fleshy, globose structures with many overlapping 



150 MANUAL OF TREE DISEASES 

shelves borne on branches arising from a single central stalk. 
For further details concerning this heartwood-rot, see under 
oak diseases, page 259. 

White Piped Butt-Rot 

Caused by Polyporus croceus Fries 
(= P. Pilotce Schw.) 

The heartwood of the base of chestnut and oak is often 
attacked by this white piped-rot. It is also occasionally 
found in the tops of the trees. The rot extends into the roots 
and is one of the most destructive wood-rots of the butts of 
oak in the Ozark Mountains. This disease has been found in 
chestnut and oak in various localities in eastern and central 
United States and probably is generally distributed over this 
area. When chestnut trees have dead limbs in the top, the 
decay may be found in the upper portion of the trunk. The 
coppice method of reproduction of the chestnut is responsible 
for the prevalence of this rot in the base of the trees. 

Symytoms. 

The affected wood is at first brownish and water-soaked. 
Later white areas appear between the spring- and summer- 
wood. These areas become larger and the wood between is 
firm and dark brown. Finally the white areas enlarge and 
become hollow cavities with white margins. The brown wood 
between the pockets at this stage is brittle and breaks apart 
easily into concentric layers. The sporophores of the causal 
fungus are buff- or orange-colored and are found sometimes on 
living trees or on fallen trees and old logs. They are soft and 
watery annual shelf-like bodies, three to six inches across. 

Cause. 

The white piped butt-rot of chestnut and oak is caused by 
Polyporus croceus or Polyporus Pilotce. Infection usually 



CHESTNUT DISEASES 151 

occurs at the base of the tree through the connection of the 
coppice sprouts with the old stumps. For further details 
concerning the Hfe history of wood-rotting fungi and the nature 
of the decay process caused by these fungi, see page 64. 

References 

Long, W. H. Three undescribed heart-rots of hardwood trees, es- 
pecially of oak. Jour. Agr. Res. 1 : 109-128, pis. 7-8. 1913. 

Schrenk, Hermann von, and Spaulding, P. Piped-rot of oak and 
chestnut. In Diseases of deciduous forest trees. U. S. Dept. 
Agr. Bur. PL Ind. Bui. 149: 39-40, pi. 5. 1909. (Note: The 
piped-rot of oak described is due to P. Rheades and of chestnut 
to P. croceus.) 



CHAPTER XVII 



ELM DISEASES 




Fig. 21. — Leaf-spot of elm. 



The elms (Ulmus) are 
common forest and orna- 
mental trees east of the 
Rocky Mountains. They 
are exceptionally free from 
specific diseases caused 
by parasites. Wound-rots 
and slime-flux are common 
in the crotches of the large 
limbs. Chaining is often 
necessary to prevent split- 
ting at the crotches. 

Leaf-Spot 

Caused by Gnomonia ulmea 
(Sacc.) Thiim. 

This is the most com- 
mon of the leaf-spot dis- 
eases of elm. In wet 
seasons, the spots become 
so abundant that defolia- 
tion results. The fungus 
causing this disease usu- 
ally occurs abundantly 



152 



ELM DISEASES 



153 



every season on the leaves in late autumn just before the 
leaves fall. 

The first indications of the spots are seen on the upper surface 
of the leaf. The dead leaf-tissue is grayish, and either scat- 
tered over the spot or 
grouped in the center are 
one or more black pustules 
(Fig. 21). The under sur- 
face of the leaf shows no 
evidence of the spot until 
later in the season, when 
brown dead areas appear 
with a few raised pustules. 

After the leaves fall to 
the ground, fruiting-bodies 
containing ascospores de- 
velop which are the source 
of primary infection the 
following spring. The 
pycnidia of many species 
of fungi are found on elm 
leaves and it is not known 
which one of these is con- 
nected with the Gnomonia. 
For a further discussion of 
leaf-spots and their con- 
trol, see page 27. Fig. 22. — Powdery mildew of elm. 

Powdery Mildews 

Caused by Uncinula macrospora Peck, Microsphcera alni (Wallr.) 
Salmon and Phyllactinia corylea (Pars.) Karst. 

Three species of the powdery mildew fungi attack the leaves 
of elms in the United States. In the case of all three species 
the characteristics, so far as visible to the unaided eye, are 




154 MANUAL OF TREE DISEASES 

similar. The first two species mentioned above occur on both 
sides of the leaf, while the last usually affects only the under 
side. The spots are usually not distinct and the mycelium may 
be only slightly noticeable (Fig. 22). The black fruiting- 
bodies are formed in patches or scattered over the leaf in all three 
species but require microscopic examination to determine their 
specific characters. The life histories and methods of control 
of the powdery mildew fungi are discussed on page 37. 

Brown Wood-Rot 

Caused by Pleurotus ulmarius Bull. 

The white elm is often affected by this brown wood-rot. The 
toadstool fruiting-bodies of the causal fungus are commonly 
seen in the autumn projecting from pruning wounds and crotches 
between limbs. The heartwood is first affected and later the 
decay extends into the sapwood. The wood becomes brown 
and is easily separated into its respective annual rings. The 
celWalls of many of the fibers of the wood are destroyed or 
partially delignified. 

The sporophores of the fungus are large, fleshy annual struc- 
tures attached to the wood of the tree by a long and more or 
less eccentric stalk. The top is convex, smooth, and varies 
from white to yellow or brown. On the under surface are 
many radiating gills or pendent plates which are notched at 
the point of attachment to the stalk. It is on these gills that 
the spores are formed. 

Reference 

Learn, C. D. Studies on Pleurotus ostreatus Jacqu. and Pleurotus 
ulmarius Bull. Annales Mycol. 10 : 542-556, pis. 16-18. 1912. 



CHAPTER XVIII 
FIR DISEASES 

The firs are important forest-trees of western and north- 
eastern United States. The balsam and Fraser fir are the only 
native species in the East. Several species are common in the 
West. The Douglas spruce or fir of western United States is also 
considered in this chapter for convenience. Many native and 
exotic species of fir are extensively used as ornamentals through- 
out the country. 

The word " fir " is properly restricted to the genus Abies, 
with erect cones and flattish leaves, and the word "spruce" 
to the genus Picea with cones mostly becoming pendulous 
and keeled leaves. The red fir or Douglas spruce is of the 
genus Pseudotsuga. 

Fir is particularly subject to diseases of the wood. Many 
of the wood-rotting fungi which attack fir are also equally de- 
structive to pine, spruce, larch and hemlock. The root-rots 
common to conifers also cause considerable damage to fir 
wherever it grows. In western United States the dwarf mistle- 
toes seriously deform the fir. Besides these important dis- 
eases, the fir is occasionally aft'ected by leaf blister-rusts, leaf- 
cast, rust witches'-broom and the gray mold twig-blight. These 
diseases are limited in their distribution by various environ- 
mental and host relations. 

Leaf Blister-Rusts 

Caused by species of Uredinopsis, Pucciniastrum and Calyptospora 

Several very similar blister-rust diseases of the needles of 
fir (Abies and Pseudotsuga) are found in the United States. 

155 



156 MANUAL OF TREE DISEASES 

In all these diseases the general symptom is the production 
from the under surface of the needles in early summer of white 
bladdery pustules or blisters. Although found rather commonly 
throughout the range of the firs, none of these diseases is known 
to cause any great damage. A yellowing of the foliage and 
defoliation may occur at times. The different species of rust- 
fungi causing these diseases require certain other kinds of 
plants on which to complete their life history. In all the species 
the spores (seciospores) developed in the white blisters on the 
fir cause the infection of the other host plant if it is in the close 
vicinity. On this second host urediniospores are formed in 
small reddish or yellowish spots in midsummer and in the 
autumn the teliospores develop either within the epidermal cells 
or on the outside of the leaf or stem. The teliospores over- 
winter and germinate in the spring, producing basidiospores 
which when blown to the fir infect the young needles. 

Fern rust. 

The most common and generally prevalent of the blister- 
rust fungi of fir needles have alternate stages on species of ferns 
and belong to the genus of fungi known as Uredinopsis. The 
blister-stage on the fir needles is known as Peridermium halsa- 
meum Peck and P. psei(do-baIsameiim, (D. and H.) Arthur and 
Kern. These rusts occur on balsam fir in the northeastern 
states and on Alpine, grand and noble fir in the Northwest. 

Recent investigations have shown that these blister-rusts are 
the alternate stages of five previously recognized species of 
Uredinopsis on ferns as follows : — 

U. osmundce Magn. on species of Osmunda ; 

U. mirabilis (Peck) Magn. on species of Lorinseria and Onoelea ; 

U. struthiopteridis Stromer on species of Anchistea and Matteuecia ; 

U. phegopteridis Arthur on species of Phegopteris ; 

U. Atkinsonii Magn. on species of Asplenium and Dryopteris. 

These rusts are not distinguishable from one another in the 
aecial stage on the fir needles, and further investigation may 



FIR DISEASES 157 

prove that they should be reduced to one species with racial 
differences as to the fern hosts preferred. 

A very similar blister-rust of the second-year needles occurs 
in the northwestern states on Alpine and grand fir and has 
been found to be due to Uredinopsis pteridis Weir and Hubert 
on species of Pteridium. The life history of this species is 
different from those above mentioned in that the teliospores 
do not over-winter. The basidiospores form in late summer 
but the fir needles infected in the autumn do not show the 
white blisters until early the following spring. 

In the other species the young newly formed needles are 
infected in the spring by basidiospores from over-wintered 
teliospores, and the white blisters are formed later in the same 
season. On the fern leaves the urediniospores show as yellow 
or brownish rust-spots. 

Fireweed rust. 

Another of the white blister-rusts occurring to some extent 
on fir needles in this country as well as in Europe is caused by 
Pucciniastrum puMulatum (Pers.) Dietel. This pathogene 
has its uredinial and telial stages on species of Epilobium, es- 
pecially E. angustifoUum, the great willow-herb or fireweed. 
Although the fungus occurs on several species of Epilobium, 
teliospores are known certainly to occur only on E. angusti- 
foUum. 

Blueberry rust. 

A common blister-rust of fir needles in Europe is caused by 
Calyptospora columnaris (Alb. and Schw.) Kiihn. It has its 
alternate stages on species of Vaccinium. On these latter 
plants the stems are attacked and become swollen. The in- 
fected stems grow erect and become much taller than sur- 
rounding bushes. The stems are at first reddish and later 
become brown or black. The teliospores are formed in the 



158 MANUAL OF TREE DISEASES 

epidermal cells of the stems and over-winter there. The 
germ-tubes bearing basidiospores are pushed out the fol- 
lowing spring and infection of the fir needles is accomplished 
when the basidiospores are blown to them. The white blisters 
appear on the needles in late spring. The affected needles 
may appear yellowish and usually drop off in late summer. The 
blister-stage on the fir is known as Peridermium columnar e 
Schmidt and Kuntze. This fungus is common throughout the 
United States on blueberry but is rarely found on firs. 

Unconnected rusts. 

Two blister-rust fungi attacking fir needles (Abies) in north- 
western United States have been named provisionally Peri- 
dermium ornamentale Arthur and P. Ilolwayi Sydow. These 
two forms may represent only a single species, however, as 
they are very similar microscopically. The alternate stages 
of these rusts are as yet unknown. 

References 

Weir, J. R., and Hubert, E. E. Observations on forest tree rusts. 
Amer. Jour. Bot. 4 : 327-335, figs. 1-2. 1917. 

Clinton, G. P. Heteroecious rusts of Connecticut having a perider- 
mium for their secial stage. Connecticut Agr. Exp. Sta. Ann. 
Rept. 1907-1908 : 369-396, pis. 25-32. 1908. 

Arthur, J. C, and Kern, F. D. North American species of Perider- 
mium. Bui. Torrey Bot. Club 33 : 403-438. 1906. 

Eraser, W. P. Cultures of some heteroecious rusts. Mycologia 3: 
67-74. 1911. 

Eraser, W. P. Cultures of heteroecious rusts. Mycologia 4 : 175- 
193. 1912. 

Eraser, W. P. Eurther cultures of heteroecious rusts. Mycologia 6 : 
233-2.39. 1913. 

Eraser, W. P. Notes on Uredinopsis mirabilis and other rusts. My- 
cologia 6:25-28. 1914. 

Hedgcock, G. G. Notes on some western Uredinese which attack 
forest trees. Mycologia 4 : 141-147. 1912. 



FIR DISEASES 159 

Leaf-Rusts 

Caused by Melampsora arctica Rostrup and M. alhertensis Arthur 

Two species of rust-fungi cause pale yellowish or white 
pustules on fir needles. These rusts are very similar to the 
blister-rusts described above except that no bladder-like cov- 
ering is developed over the pustules. 

Willoiv rust. 

A rust of balsam fir needles similar to the blister-rusts above 
mentioned is found in eastern Canada and may occur in the 
extreme northeastern part of the United States. This disease 
is caused by Melampsora arctica Rostrup. The uredinial and 
telial stages are formed on arctic species of willow. The ba- 
sidic spores are formed in the spring from over-wintering telio- 
spores and infect the new fir needles. White pustules are 
produced on the under surface of the fir needles in- midsummer. 

Poplar rust. 

A rust of poplar leaves in northwestern United States and 
the adjacent parts of Canada has its alternate stage on fir 
(Pseudotsuga) needles causing white pustules. This fungus is 
known as Melampsora alhertensis Arthur and was previously 
called CoBoma occidentalis Arthur on Pseudotsuga mucronata. 

Leaf-Cast 

Caused by Lophodermium nervisequum Fries 

The needles of balsam fir are often killed by this disease. 
Trees of all ages are affected and complete defoliation may 
result. This is especially true of small trees. The leaves be- 
come yellow and brown during the summer and autumn. The 
fruiting-bodies of the causal fungus break through the epi- 
dermis of the brown needles in long black lines. The spores are 
mature the following spring and infection may occur during 



160 MANUAL OF TREE DISEASES 

any prolonged wet period until the spores are all disseminated. 

For further details concerning the leaf-cast diseases of conifers, 

see page 38. 

Reference 

Spaulding, P. Notes upon tree diseases in the eastern states. My- 
cologia 4 : 148-151. 1912. 

Rust Witches'-Broom 

Caused by Melampsorella elatina (Alb. and Schw.) Arthur 

This rust disease causes witches'-brooms on various species 
of fir (Abies) throughout their range in the United States. It 
also occurs commonly in Canada, Mexico and Europe. The 
young affected twigs are dwarfed and develop numerous up- 
right laterals forming a broom-like growth. If the twigs are 
infected at a place where no buds are present, only gall-like 
enlargements of the bark are formed. The fungus grows out 
into the branches and leaves of the broom. The leaves re- 
main small and yellowish. There develop in midsummer 
from the under surface of these dwarfed leaves two rows of white 
blisters. The leaves then fall, leaving the broom bare during 
the winter. New growth of the twigs and new infected leaves 
are formed the following season. In this manner the broom 
develops for several years and produces a crop of spores each 
season. 

The spores (seciospores) from the fir needles infect species 
of Alsine and Cerastium. On these plants very small orange- 
red or yellowish pustules are formed in late summer. Ure- 
diniospores are produced in these pustules which may infect 
other plants of the same species. Teliospores are formed later 
in whitish or pale reddish spots on the under surface of the leaf. 
They germinate the following spring producing basidiospores 
which may infect the fir twigs. The mycelium is perennial in 
both sorts of hosts. 



FIR DISEASES 161 

Control. 

This witches'-broom of fir may be controlled by eradicating 
all sandwort and chickweed (Alsine and Cerastium) from the 
immediate vicinity of the firs. 

Reference 

Hartig, R. iEcidium (Peridennium) elatinum. In Text-book of 
the diseases of trees, pp. 179-182, figs. 109-112. 1894. 

Gray Mold Twig-BlicxHT 

Caused by Botrytis cinerea Fries 

This disease of the current season's twigs is most important 
on Douglas fir, although other firs, pine, spruce, larch and hem- 
lock may be affected. The disease is common in certain lo- 
calities in Europe and North America, both in nurseries and 
in the forest. It has been reported as destructive, especially 
to Douglas fir in nurseries, forest plantings and to some degree 
on the older trees, in several countries of Europe. In the 
forests of northwestern United States it occurs on Douglas fir, 
grand fir, western larch and western hemlock. It has not as- 
sumed great importance in any area but causes considerable 
cumulative damage. 

Symptoms. 

The most obvious general symptom of this disease is the 
withering, curling and dying of young twigs of the season. 
Seedlings and young trees may be killed. Late in the season 
black bodies the size of a pin-head are formed on the affected 
twigs and on the leaves, especially at the base of the season's 
growth. The twigs of young pine may be dwarfed, the needles 
remaining short and the twig becoming twisted. Under moist 
conditions, a more or less luxuriant mycelial growth occurs, 
forming a gray mold over the affected leaves and twigs. 



162 MANUAL OF TREE DISEASES 

Cause. 

The gray mold twig-blight of conifers is caused by the fungus 
Botrytis cinerea. The name first given to this fungus on conifers 
was Botrytis Douglasii Tubeuf. In some publications this 
fungus is erroneously called Sclerotinia Fuckeliana (De Bary) 
Fuckel, due to a suspected connection of the Botrytis with this 
ascomycete. Spores are borne in abundance on the gray mold- 
like growth of mycelium over the affected parts. These spores 
are wind-disseminated and serve to distribute the fungus dur- 
ing the summer. The small black, more or less globose bodies 
formed on the twigs and needles are called sclerotia. They are 
resting structures composed of mycelium which is rich in re- 
serve food material and covered by a black rind-tissue of 
mycelium. The fungus over-winters in this way and many 
upright branches bearing spores are sent out from the sclerotia 
in the spring. 

The mycelium within the needles and twigs causes at first 
an enlargement of some of the tissues and later their death. 
Abundant atmospheric moisture is required for the general and 
destructive distribution of the fungus in a given region. Fogs 
are conducive to epiphytotics. This is due to atmospheric 
moisture stimulating an abundant growth of superficial my- 
celium which is necessary for the formation of the spores. Also 
these same conditions insure that a larger percentage of the 
spores can germinate and cause infection. 

Control. 

Since the severity of attack is largely dependent on a con- 
tinuously humid atmosphere, any measures which will lead to 
a greater circulation of the air will serve in a measure to control 
this disease. Damp soil and close planting should be avoided 
for the more susceptible trees. In the nursery and in young 
plantations weeds and any plants or artificial structures which 
shade the trees should be removed. 



FIR DISEASES 163 

References on Gray Mold Twig-Blight 

Weir, J. R. A Botrytis on conifers in the northwest. Phytopathology 

2: 215. 1912. 
Smith, R. E. Botrytis and Sclerotinia : their relation to certain 

plant diseases and to each other. Bot. Gaz. 29 : 369-407, pis. 

1-3, figs. 1-3. 1900. 
Tubeuf, C. F. von. Botrytis Douglasii. Eine neue Krankheit der 

Douglastanne. Beitrage zur Kenntniss der Baumkrankheiten, 

pp. 4-8, pi. 1. 1888. 

Mistletoe Burl and Witches'-Broom 

Caused by Razoumofskya Douglasii (Englem.) Kuntze 

Douglas fir is seriously damaged in northwestern United 
States by this species of dwarf mistletoe. The roots of the 
germinating mistletoe seeds enter the bark through wounds. 
Swellings of the stem and enormous brooms are formed by 
the abnormal branching from the affected parts. Burls are pro- 
duced on the larger limbs and the trunk. The general effect 
of the deformed growths is a diversion of the growth energies 
of the trees to these parts. A dwarfing of the tops and a de- 
creased amount of foliage results. Large trees are not directly 
killed by the mistletoe infestation, but the trees are suppressed 
to the degree that insects and fungi cause a higher mortality 
than in stands of normal trees. A general discussion of the 
mistletoe parasites on trees will be found on page 54. 

Reference 

Weir, J. R. Mistletoe injury to conifers in the northwest. U. S. 
Dept. Agr. Bui. 360 : 1-38, pis. 1-4, figs. 1-27. 1916. 

Pecky Wood-Rot 

Caused by Trametes pini Fries 

This wood-rot is commonly known as red-rot, ring-shake and 
peckiness, and is the most destructive wood-rot of fir, spruce, 



164 



MANUAL OF TREE DISEASES 



larch and pine in the United States. The symptoms in fir are 
similar to those in spruce which are described on page 324. The 
pockets are larger than those found in spruce and the wood is 





Fig. 23. — Pecky wood- 
rot; early stage in Doug- 
las fir. 




Fig, 24. — Pecky wood-rot in 
Douglas fir. 



largely destroyed. In Douglas fir the pockets are at first cir- 
cular white areas (Fig. 23). Later the pockets increase greatly 
in number and finally the wood is honeycombed (Fig. 24). 
Somewhat different symptoms are shown in larch and pine and 
are described on pages 215 and 291 respectively. 

The life-history, dissemination of the spores and mode of in- 
fection of the wood-rotting fungi are treated in a general discus- 
sion on page 64. 



FIR DISEASES 165 

Red-Brown Sapwood-Rot 

Caused by Fonies pinicola Fries 

The red-brown sapwood-rot is one of the most common dis- 
eases of spruce, pine, fir, larch and hemlock, wherever these trees 
grow. The fungus causing this wood-rot occurs less frequently 
in living trees than it does on dead standing trees and logs. It 
is thought that the fungus usually attacks living trees which 
are badly wounded or in generally poor health. Vigorous 
healthy trees are more rarely affected. The decay progresses 
very rapidly and the wood is reduced to a light easily pulver- 
ized mass. The wood of beech, birch, maple and other de- 
ciduous trees is also destroyed by this fungus. 

Symjjtoms. 

In longitudinal section, the first evidence of the decay shows 
as whitish spots or streaks irregularly placed. The white spots 
have reddish brown centers. At this stage the wood is punky 
and brittle. The spread of the mycelium from these centers 
soon results in a uniform red-brown, easily pulverized mass of 
loose fibers. The decayed wood shrinks in all directions, leav- 
ing numerous cracks which are filled with white mycelial felts. 
These felts are largely responsible for holding the decayed wood 
from falling to pieces. 

The fruiting-bodies of the fungus are formed abundantly 
and are the most conspicuous of the various shelf-fungi in 
coniferous forests. When growing from wounds on living 
trees, they are usually hoof-shaped. On logs and dead wood 
they are broader and thinner. The upper surface is marked 
by broad rounded concentric folds, each representing the re- 
sult of a year's growth. From the center of the top to the 
margin, the color varies from black to brown and reddish brown. 
The rounded margin is yellowish in the early summer and later 
becomes reddish yellow or deep red. The surface of this bright 



166 MANUAL OF TREE DISEASES 

colored- zone appears as if varnished. The under surface is 
yellowish brown and covered with minute pores. 

Cause. 

The red-brown sapwood-rot of conifers is caused by the 
fungus Fomes innicola. Infection occurs in wounds which ex- 
pose the sap wood of the tree. The wood fibers are not de- 
stroyed completely but are reduced to weak thin-walled struc- 
tures with numerous cracks and fissures. The life history and 
control of wood-rotting fungi is more fully discussed on page 64. 

References 

Schrenk, Hermann von. Polyporus pinieola (Swartz) Fr. In Some 

diseases of New England conifers. U. S. Dept. Agr. Div. Veg. 

Phys. and Path. Bui. 25 : 24-31, pis. 3-5, fig. 2. 1900. 
Atkinson, G. F. Polyporus pinieola. In Studies of some shade tree 

and timber destroying fungi. Cornell Univ. Agr. Exp. Sta. Bui. 

193 : 222-227, figs. 80-81. 1901. 
Hedgcock, G. G. Notes on some diseases of trees in our national 

forests. IV. Phytopathology 4: 181-188. 1914. 

Stringy Red-Brown Heartwood-Rot 

Caused by Echinodonliiim tinctorium Ellis and Everhart 

The destructive stringy red-brown heartwood-rot of fir, 
spruce and western hemlock is a common disease of these trees 
in western United States. White, Alpine, grand, noble and 
Douglas fir, Engelmann spruce and western hemlock are known 
to be affected by this wood-rot. The older stands of firs in the 
northwestern forests are so badly damaged by this rot that 
they are practically worthless. 

Syviptoms. 

The first indication of this heartwood-rot is noticeable in the 
branch stubs through which the fungus finds entrance to the 
heartwood. The wood of the branch stubs is a rusty brown 



FIR DISEASES 



167 



and from the exterior this rot is identified by the rusty knots. 
In the heartwood there are three distinct stages in the progress 
of the decay. As the rot advances, the newly afi'ected wood 
is discolored and spongy, with occasional light brown spots. 
This advance rot, as it is called, extends from two to six feet 
beyond the distinctly red-brown disorganized wood. In more 




Fig. 25. — Fruiting-body of Echinadonliuni tinctorium. 



advanced stages, the wood turns red-brown and is soggy. The 
annual rings are separated into sheets which appear as brown 
cylinders one inside the other. Soon, however, the wood of 
these partially destroyed rings is dissolved and the tree be- 
comes hollow\ The decay may proceed until only a thin shell 
of sapwood remains. 



168 MANUAL OF TREE DISEASES 

The sporophores of the causal fungus are formed at the 
rusty knots and are large hoof-shaped bodies, gray or black 
above and with numerous large and firm straw-colored or gray 
spines on the under surface (Fig, 25), The inner substance of 
the bodies is bright rusty red. The American Indian used the 
red fungous material for making war paint and thus this 
fungus has been named the Indian paint-fungus. 

Cause. 

The stringy red-brown heartwood-rot of western conifers 
is caused by Echinodontium tindorium, a member of the toothed 
fungi (Hydnaceee), The spores are borne on the outer surface 
of the teeth on the under side of the fruiting-body. Infection 
occurs when the spores lodge on the exposed wood of broken 
branch stubs. For further details concerning the life history 
and control of the wood-rotting fungi, see page 64. 

Reference 

Meineeke, E. P. Forest tree diseases common in California and Ne- 
vada. U. S. Dept. Agr. Forest Service. Unnumbered publica- 
tion, pp. 1-67, pis. 1-24. 1914. 

Brown Pocket Heartwood-Rot 

Caused by Fomes roseus Fries 

The heartwood of fir is frequently destroyed by the brown 
pocket-rot. This disease occurs also in juniper, larch, spruce, 
pine and hemlock and occasionally in arbor- vitae, beech and 
maple. Long, cylindrical and pointed pockets of brown char- 
coal-like decayed \YOod are formed. The fruiting-bodies of the 
causal fungus are either thin and shelf-like or thick and hoof- 
shaped. The under surface of the fruiting-body is rose-colored. 
This heartwood-rot is more fully described mider juniper dis- 
eases, page 204, 



FIR DISEASES 



169 



Brown Heartwood-Rot 

Caused by Fonies officinalis Fries (= Fomes laricis (Jaeq.) Murrill) 

Douglas fir is often severely damaged by this heartwood-rot 
in the Northwest. Larch, pine and other conifers are affected 
by the same disease throughout western United States. The 
decayed wood re- 
sembles the brown 
checked wood-i'ot 
caused by Poly- 
porus sulphureiis 
(see page 247). In 
the final stages of 
decay, the heart- 
wood is brownish 
or red-brown. 
Felts of mycelium 
form in checks in 
the brown wood 
(Fig. 26). The 
fruiting-bodies of 
the causal fungus 
are large hoof- 
shaped or globose, 
with a rough 
chalky upper surface. The inner substance of the sporophore 
has a bitter taste. A more complete discussion of this heart- 
wood-rot will be foimd under larch diseases, page 216. 




Fig. 26. — Brown heartwood-rot of Douglas fir. 



Brown Root- and Butt-Rot 

Caused by Fomes annosus Fries 

This rot of the wood of the roots and lower part of the 
trunk of fir is occasionally found in the forests of the North- 



170 MANUAL OF TREE DISEASES 

west. Pine, spruce and other conifers are also sometimes 
affected wherever these trees grow. The wood is discolored 
and changes from bluish to yellowish and finally becomes 
red-brown. V/hite pockets with black centers appear in the 
spring-wood of the rings. Later the pockets coalesce and the 
brown summer-wood is left in separated sheets. The peren- 
nial sporophores are shelving or resupinate and are found 
attached to the diseased roots. The upper surface of the 
shelving form is light brown and the under yellowish. For 
further details concerning this root-disease, see under spruce 
diseases on page 329. 

Red-Brown Root- and Butt-Rot 

Caused by Polyporus Schweinitzii Fries 

This root-rot occurs also on pine, larch, spruce, hemlock and 
arbor-vitse throughout the range of these trees. It is next in 
importance to the pecky wood-rot of conifers caused by Tra- 
in etes ijini. The heartwood of the roots and lower part of the 
trunk becomes at first yellowish and cheesy and later is red- 
brown and brittle, resembling charcoal in structure. This 
wood-rot is more fully discussed under pine diseases, on page 294. 

Yellow Root-Rot 

Caused by Sparassis radicata Weir 

This 3'ellow or brownish root-rot of fir, spruce, pine and larch 
has been recently described as common in northwestern United 
States. It seems to be equally as important in that region as 
the shoe-string and brown root-rots, caused by Armillaria 
mellea and Fomes annosus. The fungus causing the yellow rot 
is peculiar in having a long perennial root-like attachment of 
fungous mycelium which arises from the diseased roots. Other 
species of the same group of fungi have been suspected of calis^" 



FIR DISEASES 171 

ing root-rots of various conifers and hardwood trees but have 
never been accurately studied. 

Symptoms. 

Lateral roots are attacked even to considerable depths in the 
soil. The mycelium from the point of infection spreads out 
in the cambium and bark in yellowish fan-like plates. The 
root is girdled and killed. The mycelium then penetrates the 
sapwood, destroying first the medullary-rays. The affected 
region is bordered by a reddish zone and at times by a jet- 
black line. The heartwood at first is not penetrated because of 
its high resin-content. Certain areas of heartwood are attacked, 
however, and long pits formed by the complete destruction 
of the tissues. At other times the inner layers of heartwood 
may be largely destroyed, leaving a resinous layer of unaffected 
wood between the decayed region and the sapwood. The 
decayed heartwood is brownish or yellowish. Numerous 
delicate brown strands of mycelium penetrate the wood where 
openings have been formed. The cambium region is replaced, 
by a thick felt of mycelium. 

The fruiting-bodies of the causal fungus are formed on the 
surface of the ground. A long, fleshy, tuber-like body at- 
tached to the diseased root pushes upward through the soil and 
bears the upright fruiting-body on its tip. This fruiting-body 
is a large, fleshy, compact, whitish, much branched structm-e, 
often as much as ten inches across and equally as high. The 
branches terminate as thin leaf-like but much crumpled plates 
which stand upright or horizontally. The perennial tuber- 
like attachment to the roots is often fifteen or more inches 
long and a new fruiting-body is formed from its tip each year. 

Cause. 

The yellow root-rot of conifers is caused by the fungus 
Sparassis radicata of the family Clavariaceae. The spores are 



172 MANUAL OF TREE DISEASES 

borne over the surface of the leaf-Hke plates of the fruiting- 
body. For further details concerning the life history and con- 
trol of wood-rotting fungi, see page 64. 

Reference 

Weir, J. R. Sparassis radieata, an undescribed fungus on the roots 
of conifers. Phytopathology 7 : 166-177, figs. 1-5. 1917. 



CHAPTER XIX 
HACKBERRY DISEASES 

Two species of hackberry (Celtis) occur in eastern and central 
United States. These trees are not important forest species 
and in many sections they are shrub-Hke. West of the Missis- 
sippi River, the hackberry is commonly used for shade and 
ornament. The most important disease of this tree is the 
witches'-broom. Several leaf-spot fungi and powdery mil- 
dews are common on hackberry. Although no wood- or root- 
rots have been recorded as affecting the hackberry, doubtless 
some of the more common wood diseases of other deciduous 
trees may also be found in them. The small amount of atten- 
tion that has been given to the diseases of the hackberry is 
due to its unimportance as a timber-tree. 

Powdery Mildews 

Caused by Uncinula parvula Cooke and Peck, and Uncinula polychccta 
(Berk, and Curt.) ex Ellis 

Besides the powdery mildew fungus which is associated with 
the formation of the prominent knots and witches'-brooms, 
two other species of the same group attack the leaves of the 
hackberry. The one, Uncinula parvula, is reported through- 
out the United States, while the other species, Uncinula 
jjolychceta, is apparently confined to the southeastern states. 
The former species causes inconspicuous powdery growths on 
both sides of the leaf. The black fruiting-bodies are very 
small and usually confined to the under surface of the leaf, 

173 



174 MANUAL OF TREE DISEASES 

while in the latter species dense Irregular white patches are 
formed on the under sides of the leaves, and the black fruiting- 
bodies are large in comparison with those of the former species. 
The life histories and methods of control of powdery mildew 
fungi are discussed on page 37. 

Witches'-Broom 

Caused by a gall-mite and Sphoerotheca phytoptophila Kellerman and 

Swingle 

The hackberry is affected, in central United States, by an 
important witches'-broom disease. Although mainly impor- 
tant because of the unsightly appearance of affected orna- 
mentals, some damage to the tree must result from the loss of 
energy spent in the development of the brooms. Also due to 
the death of the branches or their breakage, wounds are formed 
which allow wood-rot fungi to enter. The lower branches are 
most commonly affected, although at times brooms are found 
throughout the crown. Hundreds of brooms are sometimes 
found on a single tree, causing serious deformation. 

Symptorm. 

Two general types of brooms are formed. The open type 
consists of irregular swellings or knots at the base of a branch 
from which many short stubby twigs arise. The leader remains 
healthy, however, and grows to its normal length and other 
knots with diseased laterals are formed on it at intervals. A 
closed type of broom results when the leader is diseased and 
fails to develop normally. For several years, after the first 
knot with its diseased laterals is formed, the new laterals from 
the base of those of the previous year cause a compact broom 
of many deformed and dwarfed branches all arising from a 
large irregular mass of gall-tissue. Smaller galls may be de- 
veloped also further out on the diseased laterals. 



HACK BERRY DISEASES 175 

The first indication of the diseased condition can be detected 
by examining the buds in the winter. Diseased buds are 
found on wood one year or more old. They are larger in diame- 
ter than healthy buds of the same length, grayish in color and 
more open and hairy. When closely examined, it is seen that 
the scales and inner bud-parts are distorted and enlarged, 
causing the scales to stand open, exposing the inner parts. 
Inside of the scales small mites are found. The mycelium of 
the mildew fungus covers the outsides of the scales and the 
small black fruiting-bodies of the mildew may be found within 
the bud on the inner scales and young leaves. The buds of 
the diseased laterals are more numerous than is normal and they 
are usually all diseased. ]\Iany diseased buds are formed at 
the bases of these laterals from which develop a new knot 
with stubby dwarfed branches. The mycelium of the powdery 
mildew fungus covers the buds and twigs early in the spring 
and even at times is found on the under sides of the leaves of 
diseased branches. This causes a whitish powdery appear- 
ance of these parts. 

Caiise. 

Two causal agents are always associated with the diseased 
buds which develop the knots and broom-like growths. One 
is a gall-mite, a species of Phytoptus, and the other a powdery 
mildew fungus, SphcBrotheca yhytoptophUa. It has never 
been definitely determined which of these two agents is the 
more responsible in producing the abnormal growths. The 
gall-mites are known to cause galls and warts of leaves and 
twigs and in some instances other powdery mildews have been 
found growing on the diseased areas produced by these insects. 
Since, however, the mildew fungus is found growing over and 
within the diseased buds and the fruiting-bodies are already 
fully formed within the unopened buds, it seems reasonable to 
believe that the fungus is present from the very initiation of 



176 MANUAL OF TREE DISEASES 

the diseased condition and may be jointly responsible for the 
deformation. Two such intimately associated agents, one an 
insect and the other a fungus, are unusual and deserve more 
careful study than has been given them. Practically nothing 
is known concerning the life history of these two parasites and 
their interrelations, more than has been discussed under symp- 
toms. Both conidia and perithecia are formed by the mil- 
dew fungus. The structure, life history and control of the 
powdery mildew fungi are more fully discussed on page 34. 
In the case of this disease, control measures seemingly would 
be confined to cutting out the diseased twigs and brooms. 
Spraying or dusting could not be expected to yield satisfactory 
results. 

References 

Kellerman, W. A., and Swingle, W. T. Branch knot of the hackberry. 

In Report of the Botanical Department. Kansas Agr. Exp. Sta. 

Ann. Rept. 1 : 302-315, pis. 4-6. 1889. 
Halsted, B. D. Notes upon Sphserotheca phytoptophila Kell. and 

Swingle. Jour. Mycology 5:85-86. 1889. 
Salmon, E. S. Sphserotheca phytoptophila Kellerm. and Swingle. 

hi A monograph of the Erysiphaceae. Mem. Torrey Bot. Club. 

9 : 76-79. 1900. 



CHAPTER XX 
HEMLOCK DISEASES 

Four species of hemlock or Tsuga occur in the forests of the 
United States. The two eastern hemlocks are important trees, 
especially in the northeastern states. The western species are 
confined to the northwestern states and are large trees. All 
four species are frequently used as ornamentals. 

Although several fungous diseases are occasionally found on 
hemlock, it is less severely affected in general than pine, spruce 
and fir. In the Northwest, the young trees are killed by a 
root-rot and the older ones are often afPected by the stringy 
red-brown heartwood-rot. In the East, the leaf-blight, rusts 
and wood-rots cause but little damage. 

Seedling Root-Rot 

Caused by Rhizina undulala Fries 

The roots of three- to five-year-old seedlings of species of 
hemlock, pine, larch and fir are frequently attacked in the 
forests of the Northwest by Rhizina undidata. The fungus 
has been found in several eastern states attached to roots of 
conifers but its connection with any root disease is not definitely 
established. The same disease is common in Europe on seed- 
lings of various conifers and has been known for many years. 

SyTrfptoms. 

The fruiting-bodies of the fungus are formed annually and 
grow on the surface of the ground. They are variable in size, 
measuring often two or three inches across, irregular in shape, 
N 177 



178 MANUAL OF TREE DISEASES 

with an undulating, rich brown upper surface bordered at the 
margin by a narrow white zone (Fig. 27). In wet weather the 
upper surface becomes mucilaginous. The under surface is 
more or less fused with the soil. Long white strands of my- 
celium, arising from the under surface, can be traced to diseased 
roots. Affected seedlings growing in nursery-beds or in the 
forest are killed in isolated groups. On pulling the trees, the 
roots are found to be closely matted with white mycelium. 
This characteristic, together with the soil being held together 
by the matted mycelium and the roots being more or less 
resinous, make this root disease practically indistinguishable 




Fig. 27. — Fruiting-bodies of Rhizina undulata. 

from the common shoe-string root-rot caused by Armillaria 
mellea. This latter fungus is common as a root-rotting fungus 
of both conifers and deciduous trees and sometimes attacks 
young seedlings (see page 78). Often, however, the fruiting- 
bodies of the Rhizina occur plentifully around and envelop the 
stems of affected seedlings. 

Cause. 

The pathogene causing this seedling root-rot is an ascomy- 
cetous fungus which forms spores in closely packed asci. These 
stand upright and form the brown upper surface of the fruiting- 
body. The spores are forcibly shot upward into the air and are 
blown away. Falling on the ground, they germinate and the 
abundant white mycelium that is formed penetrates the root- 
tissues and causes the seedling to die. 



HEMLOCK DISEASES 179 

Control. 

No specific measures of control have been tried, so far as 
known. The control measures given on page 81 for the shoe- 
string root-rot may be applied to this disease as well. 

References 

Weir, J. R. Observations on Rhizina inflata. Jour. Agr. Res. 4 : 

93-95, pi. 8. 1915. 
Hartig, R. Rhizina undulata Fr. the root fungus. In Text-book 

of the diseases of trees, pp. 123-129, figs. 61-70. 1894. 

Leaf-Blight 

Caused by Keithia tsugce (Farlow) Durand 

The leaves of the eastern hemlock are at times killed by this 
leaf-blight. Instances are reported in which several trees 
were almost defoliated. This disease is definitely reported 
only from New Hampshire, Massachusetts and Wisconsin. 
It may, however, be found at other places in the range of the 
hemlock. The leaves that are affected turn brown and fall from 
the twigs. These symptoms occur in the late summer. The 
fruiting-bodies of the pathogene form during the summer on the 
affected leaves. They appear as small black pustules bursting 
through the leaf-epidermis. Ascospores are forcibly ejected 
from these fruiting-bodies during moist weather. Additional 
facts concerning the life history of this fungus will be found 
on page 90, where a similar disease of western arbor-vitse is 
discussed. 

References 

Durand, E.J. The genus Keithia. Mycologia 5 : 6-11, pi. 81. 1913. 
Farlow, W. G. Notes on the cryptogamic flora of the White mountains. 

Appalachia 3 : 245-246. 1883. 
Spaulding, P. Diseases of the eastern hemlock. Proc. Soc. Amer. 

Foresters 9 : 245-256. 1914. 



180 MANUAL OF TREE DISEASES 

Brown-Mold Leaf-Blight 

Caused by Rosellinia sp. ? 

The importance and prevalence of this disease of hemlock 
is so far not known. It has been found in North Carolina. 
The needles of the lower branches become yellow. The af- 
fected twigs show a growth of yellowish-brown or grayish 
mycelium covering the bark and investing the bases of the 
yellow needles. The dead needles either fall off or are held 
by the tangle of mycelium. Small dome-shaped fruiting- 
bodies of the fungus are found slightly sunken in the mycelium. 
Although not definitely determined, this fungus apparently 
belongs to the genus Rosellinia. It has not yet been definitely 
established that the brown mycelium is directly responsible 
for the diseased condition. 

Reference 

Graves, A. H. Notes on the diseases of trees in the southern Appa- 
lachians III. Phytopathology 4 : 63-72, pi. 5, fig. 1-10. 1914. 

Leaf and Cone Blister-Rusts 

Caused by Pucciniastrum viinimum (Sehw.) Arthur, and P. myrtilli 
(Sehum.) Arthur 

Two species of the blister-rust fungi attack the green parts 
of the eastern and Carolina hemlock. These rusts are very 
similar in appearance and have been found in widely separated 
localities throughout the range of the two eastern hemlocks. 
The leaves and cones may be at times so heavily infected 
that the leaves fall and the cones fail to mature viable seeds. 
This happens only in the case of individual trees which stand 
close to the alternate host plants which these fungi require for 
the completion of their life history. 



HEMLOCK DISEASES 181 

Syinjytoms. 

Although these two species of fungi differ sufficiently so 
they can be recognized by their microscopical characters, the 
general appearance of fruiting-structures and the effect on 
the tree is very similar. The leaves of young trees or of 
the lower limbs of older trees are much oftener affected than 
the tops of older trees. Sometimes one-half of the cones 
may be affected. The most conspicuous symptom of these 
diseases is the production, on the leaves or cones of golden- 
yellow or reddish colored blisters in June and July. These 
blisters burst through the epidermis of the aflFected parts and 
when abundant their color stands out prominently against the 
dark green of the healthy foliage. The spores borne in the 
blisters sift out as a fine powder and are blown away by the 
wind, 

Catise. 

Two species of the rust-fungi are known to cause the blister- 
rust of the leaves and cones of hemlock. The life history 
of these species varies slightly in that different kinds of 
shrubs are required for their further development. 

The first species mentioned, Pucciniastrum minimum, occurs 
on the leaves and cones. This fungus was known on 
the hemlock previously as Periderinium Peckii Thiimen. 
The spores from the blisters on the leaves cause the in- 
fection of the leaves of species of Rhododendron. On 
this host plant, very small yellowish spots are developed on 
the under sides of the leaves. The spores produced in early 
spring on the rhododendron leaves infect the newly developed 
leaves and cones of the hemlock. 

The second species, Pucciniastrum myrtiUi, is known to occur 
only on the leaves. This fungus was also previously known as 
Peridermimn Peckii. The blisters on the hemlock leaves 
are more reddish than those of the other species. The 



182 MANUAL OF TREE DISEASES 

spores from the blisters infect the leaves of species of blue- 
berry. On this host plant are formed small yellowish spots 
on the under sides of the leaves. Later light brown spots 
appear in the same areas. The spores produced the following 
spring from the brown spots cause the infection of the young 
hemlock leaves. 

Control. 

By keeping rhododendrons and blueberry bushes away from 
hemlock trees, these blister-rusts can be prevented. The 
heaviest infection of the hemlock occurs when one of these 
alternate host plants stands within a few feet. 

Reference 

Spaulding, P. Diseases of the eastern hemlock. Proc. Soe. Amer. For- 
esters 9 : 245-256. 1914. (Bibliography given.) 

Leaf-, Cone- and Twig-Rusts 

Caused by Melampsora abietis-canadensis (Farl.) Ludwig, and Neciiim 
Farlowii Arthur 

In addition to the two blister-rusts of hemlock (page 180) 
two other rust-diseases occur on these trees. In Nova Scotia 
instances have been noted in which the leaves and twigs of 
the entire top of the tree were killed by the later fungus. 

Symptoms. 

The first species, M. abietis-canadensis, causes a rust on the 
leaves, cones and twigs similar in appearance to the blister- 
rusts. This fungus was known on the hemlock previously 
as Coeomu abietis-canadensis on the leaves and as Peri- 
dermium fructigenum on the cones. The spores from the 
pustules produced in early summer on the affected parts 
of the hemlock cause the infection of the leaves of the large- 
tooth aspen. On this second host small orange or brown- 



HEMLOCK DISEASES 183 

ish spots are produced on the leaves. Later reddish brown 
pustules are formed (see page 298). Spores formed on the 
dead aspen leaves the following spring, when blown to the 
hemlock, cause the infection of the young green parts. 

The leaves and twigs affected by the second species, Necium 
Farlowii, may die in midsummer, the leaves falling off. When 
defoliation does not take place, the infected leaves and twigs 
bear reddish, swollen, velvety pustules in early spring. The 
cones may show the same reddish bodies. 

Cause. 

These rust-fungi are close relatives of the hemlock blister- 
rusts. The first species produces eeciospores in open pustules 
which do not have a bladdery covering, as in the blister-rusts. 
The second species does not produce eeciospores but forms 
teliospores as its only spore-stage. These over-winter and 
burst the epidermis, producing reddish waxy pustules in the 
spring. The basidiospores produced by the germination of 
the teliospores reinfect the young green parts of the hemlock. 
Thus this rust-fungus requires no alternate host and occurs 
only on the hemlock. 

Control. 

The rust having its alternate stage on poplar leaves may 
be controlled by keeping poplars separated from hemlocks by 
a few hundred feet. In the case of the second fungus, which 
occurs only on hemlock, the affected twigs should be pruned off 
in the winter and burned, thus destroying the spores of the 
fungus and preventing further infection. 

Reference 

Ludwig, C.A. Notes on some North American rusts with Cseoma-like 
sori. Phytopathology 5 : 273-281. 1915. 



184 MANUAL OF TREE DISEASES 

Red-Brown Sapwood-Rot 

Caused by Fomes pinicola Fries 

Hemlock is sometimes affected by this sap wood-rot. It 
occurs also in spruce, pine, fir and larch. Coniferous wood of 
all kinds is destroyed by the fungus causing this rot, and the 
sporophores are very abundant on fallen logs and dead stand- 
ing trees. The wood is reduced to a red-brown powdery mass 
held together by numerous plates of mycelium. The sporo- 
phores have a red varnished margin and a cream-colored under 
surface. Further details concerning this wood-rot will be 
found under fir diseases, page 165. 

Stringy Red-Brown Heartwood-Rot 

Caused by Echinodontium tinctorium Ellis and Everhart 

The western hemlock is destructively affected by this heart- 
wood-rot. Firs and spruce are also commonly decayed by the 
same fungus. In the first stage of decay, the wood is discolored 
and spongy. The wood then becomes red-brown and the 
spring-wood of the annual ring is dissolved, leaving the summer- 
wood in separated cylinders one inside of the other. Later 
these sheets of summer-wood are destroyed and the tree be- 
comes hollow. For further details concerning this heartwood- 
rot, see under fir diseases, page 166. 

Brown Pocket Heartwood-Rot 

Caused by Fomes roseus Fries 

The eastern and western hemlock are sometimes affected 
by this heart wood-rot, which is also found in juniper, fir, larch, 
spruce, pine and occasionally in arbor-vitse. It occurs prac- 
tically throughout the entire country wherever conifers are 
important forest-trees. Long, cylindrical and pointed pockets 



HEMLOCK DISEASES 185 

of brown charcoal-like rotted wood are formed in the heart- 
wood. The fruiting-bodies of the causal fungus vary from small 
thin shelves to larger hoof-shaped bodies. The upper surface 
is black in the older fruiting-bodies, while the new layer of 
tubes on the under surface is rose-colored. For further details 
concerning this heartwood-rot, see under juniper diseases, 
page 204. The fungus continues to grow in fallen trees and 
the fruiting-bodies are more commonly found on dead wood 
than on living individuals. The sapwood is also decayed in 
dead trees and logs. 

CuBoiDAL Wood-Rot 

Caused by Polyporus horealis Fries 

This heartwood-rot does not seem to occur abundantly, 
since but little mention of it is found in literature. It is re- 
ported in New York but no definite statements on its importance 
and range are available. Red spruce is also known to be 
affected by this wood-rot. 

Symptoms. 

In the early stages of the decay, long parallel strands or cords 
of white mycelium, lying close together, push their way through 
the wood in the radial and tangential directions. The white 
strands then disappear, leaving channels in the wood. Because 
of these perforations and the shrinkage of the wood, it breaks 
into minute cubes. On the border of the affected wood, the 
mycelium reaches out into the normal wood in very fine strands. 
These then develop into the thicker white cords described 
above (Fig. 28). 

The fruiting-bodies are formed on the trunk or at the base 
of the tree. Usually several shelf-like bodies one above the 
other occur together, forming a cluster. The upper surfaces 
of the shelves are white and shaggy. The under surfaces are 



186 



MANUAL OF TREE DISEASES 



covered with small roundish or sinuous openings. The entire 
fruiting-body is white or yellowish and soft and spongy. 

Cause. 

The cuboidal wood-rot of hemlock and spruce is caused 
by the fungus, Polyporus horealis. The spores from the tubes 
opening on the under side of the fruiting-body are blown about 
by the wind. Infection takes place at wounds. The heart- 




FiG. 28. — Cuboidal wood-rot of hemlock. 

wood may be affected from the top to the base of the tree. 
The sapwood is decayed and the smaller limbs killed at the top 
of the tree. For further details concerning the life history and 
control of wood-rotting fungi, see page 64. 

References 

Atkinson, G. F. Polyporus borealis. In Studies of some shade tree 
and timber destroying fungi. Cornell Univ. Agr. Exp. Sta. Bui. 
193: 202-208, figs. 56-63. 1901. 

Hartig, R. Polyporus borealis Fr. In Die Zersetzungserscheinungen 
des Holzes etc., pp. 54-58, pi. 10. 1878. 



HEMLOCK DISEASES 187 

Red-Brown Root- and Butt-Rot 

Caused by Polyporus Schweinitzii Fries 

In addition to hemlock, this root- and butt-rot occurs in 
fir, pine, larch, spruce and arbor-vitse. It is a destructive 
root-disease of these trees throughout their range. The affected 
wood is first yellowish and cheesy, later changing to a red- 
brown, uniform rot. The completely decayed wood is brittle, 
and is similar in appearance to charcoal. For a more complete 
description of this disease, see page 294. 



CHAPTER XXI 

HICKORY DISEASES 

Several species of hickory (Carya or Hicoria) occur as com- 
mon trees in eastern United States. Several fungi cause leaf- 
spots of hickory (page 30). Besides these, the leaf-mildew, 
witches '-broom and common white wood-rot are the only dis- 
eases of importance of these trees. Although these diseases 
and probably others are common on hickory practically no 
mention of them is made in literature. 

Leaf-Mildew and Witches'-Broom 

Caused by Microstroma juglandis (Bereng.) Saec. 

The leaves of hickory and walnut in eastern United States are 
often affected by this disease. Early in the summer the leaflets 
show a white powdery mildew on the under side. The invaded 
area of the leaflet is yellowish and defoliation may result. Re- 
cently the formation of witches'-brooms on shag-bark hickory 
has been shown to be another symptom of this disease. Brooms 
are sometimes numerous on the trees and are as much as a yard 
across. The leaves which appear on the brooms in the spring 
are yellowish green above and covered with the white powdery 
growth of the fungus below. The leaflets are smaller than nor- 
mal and curled. They fall prematurely and leave the brooms 
bare in midsummer. The fungus causing this disease is sup- 
posed to be a simple basidiomycete forming numerous short 
stalks bearing spores on the under sides of the leaf. 

188 



HICKORY DISEASES 189 

Reference on Leaf-Mildew and Witches'-Broom 

Stewart, P. C. Witches-brooms on hickory trees. Phytopathology 
7: 185-187, fig. 1. 1917. 



Common WraTE Wood-Rot 

Caused by Fomes igniarius Fries 

The heartwood of hickory is sometimes reduced to a white 
soft punk by the false-tinder fungus. This rot is more common 
and destructive to beech, poplar, oak and maple. The sporo- 
phores and appearance of the white rotted wood are described 
under poplar diseases, page 305. 



CHAPTER XXII 
JUNIPER DISEASES 

Several species of juniper (Junipems) occur as important 
forest-trees over the entire United States. These trees and the 
horticultural varieties of the native and exotic species are the 
most common conifers used for ornament. In the genus 
Juniperus are included the low junipers. 

The juniper is subject to several important wood-rots and 
rust-diseases. Several destructive heartwood-rots of juni- 
per are especially common in the Southwest. The rust- 
diseases of juniper are important both from the economic 
and ornamental standpoint. Many of the rust-fungi be- 
longing to the genus Gymnosporangium grow parasiti- 
cally in the leaves, branches or trunk of juniper. Several 
types of over-growth occur in the affected tissues. These 
diseases are interesting because of the complicated life history 
of the different species requiring various other plants as alter- 
nate hosts. As certain of these fungi cause the rust-diseases of 
apple, pear and quince, their control is an orchard as well as an 
ornamental tree problem. 

Seedling Twig-Blight 

Caused by Phoma sp. 

Junipers grown in nursery-beds are subject to a twig-blight 
which has been destructive in certain seasons in Kansas, Ne- 
braska, Iowa, Illinois and Pennsylvania and may be expected 
in other localities. By artificial inoculation with the causal 

190 



JUNIPER DISEASES 191 

fungus, the same disease has been found to affect several 
species of juniper, arbor-vitae and cedar. Wet seasons are 
conducive to epiphytotics of this disease, but it seems never 
to affect trees more than three or four years old. 

Symptoms. 

This twig-bhght may appear at any time and continue to 
spread throughout the growing season on nursery stock less 
than four years old. When severe, entire beds of stock may be 
destroyed. The general appearance of the trees is not unlike 
that produced by sun-scorch, except that the trees of a given 
bed are not affected uniformly but die in spots, which are ir- 
regular in outline and gradually increase in size. The small 
lateral branches are affected first and soon are killed. The 
mycelium then extends its growth into the main stem and 
spreads more rapidly upward than downward. Other lateral 
twigs may thus become affected and killed before the main stem 
is girdled. Recently killed laterals show bleached lesions of a 
purplish or grayish cast at the base where they branch from the 
main stem. When the main stem is affected and it is cut length- 
wise with a knife, the cambium and wood are seen to be discolored. 
Girdling is sometimes not accomplished and the long sunken 
cankers heal over, leaving a flattened stem. The terminal is 
often killed directly by the mycelium spreading upward into it 
before girdling has taken place. jNlinute black fruiting-bodies 
break through the epidermis of the leaves and bark even before 
any outward discoloration is apparent. In moist weather, 
prominent hair-like twisted tendrils composed of hundreds of 
the spores of the fungus are pushed out from these fruiting- 
bodies. 

Cause. 

The twig-blight of seedling junipers and other conifers is 
caused by a fungus of the genus Phoma. Only the one type of 



192 MANUAL OF TREE DISEASES 

frulting-stage, as described under symptoms, is known. Spores 
are produced in abundance from the fruiting-bodies (pycnidia) 
during wet weather and may be washed or spattered by rain to 
neighboring trees. The first infections take place in the lateral 
twigs, which are quickly killed. The mycelium then spreads 
into the main stem and proceeds upward, killing the outer wood- 
tissues and cambium on one side of the tree and running out 
into other laterals. 

Control. 

Experiments so far tried in spraying with lime-sulfur and bor- 
deaux mixture for the control of this disease have not been suc- 
cessful. The period of infection extending throughout the grow- 
ing-season and the nature of the scale-like leaves and the twigs 
preclude much hope of good results from spraying. Careful 
eradication of all diseased and neighboring trees may, to some 
extent, reduce losses by stopping the enlargement of the spots 
in the beds. 

Reference 

Hahn, G. G., Hartley, Carl, and Pierce, R. G. A nursery blight of 
cedars. Jour. Agr. Res. 10 : 533-539, pis. 60-61. 1917. 

Leaf- and Stem-Rusts (General) 

Caused by species of Gymnosporangium 

Several species of the rust-fungi belonging to the genus Gym- 
nosporangium cause more or less important diseases of juniper 
and cedar. These fungi are strictly parasitic and never grow 
except in the living tissue of some plant. They are, therefore, 
confined to the range of the species of juniper and cedar, which 
are found in the north temperate zone in North America, 
Europe, Asia and northern Africa. Another important pe- 
culiarity of these fungi which further restricts the range of each 
species is that they each require certain kinds of broad-leaf trees 



JUNIPER DISEASES 193 

and shrubs as alternate hosts. Unless the necessary alternate 
host is present in close proximity to the juniper or cedar, the 
rust cannot exist, since the life history of the fungus cannot be 
completed. Trees and shrubs of the order Rosales, family 
Pomacese, are the most common alternate hosts of these fungi. 

The life history of all the Gymnosporangium rusts is similar 
and is described here to avoid repetition below. As stated, these 
fungi are parasitic throughout their life. They live for a time 
on a certain species of juniper or cedar and produce spores 
(basidiospores) which can only cause infection of the leaf, twig 
or fruit of a certain few or perhaps only a single species of the 
wild or cultivated apple-like trees, such as apple, pear, quince, 
haw, mountain ash and service-berry. Here the fungus lives 
only for a short time and produces spores (seciospores) which 
do not reinfect other trees of the same kind but can only infect 
the required juniper or cedar. Thus it is seen that the spores 
produced on each of the two kinds of hosts are innocuous to the 
same host and must find lodgment on trees of the other type in 
order to continue the life history. 

These rust-fungi over-winter as mycelium in the juniper or 
cedar leaves or stems. The next season after infection occurs, 
most of these fungi cause some type of over-growth of the tissues. 
Such abnormalities are brought about as long swellings or glo- 
bose galls on the stems, watches'-brooms and leaves transformed 
into brown globose growths known as cedar-apples. A few of 
the species cause no abnormal growth and are evident only by 
the fruiting-structures. The fungi form spores (teliospores) in 
the early spring on masses of mycelium pushed out from the bark 
of the twig or epidermis of the leaf. These spore-masses may 
be in the form of cushions or ridges in the crevices of affected 
bark or, in the case of the cedar-apples, they consist of long 
horn-like projections, sometimes an inch or more in length. 
They appear at first dark brown, due to the color of the telio- 
spores on the surface. In wet weather the spore-masses become 
o 



194 



MANUAL OF TREE DISEASES 



jelly-like and the individual spores germinate, each producing 
several secondary spores (basidiospores) which are shot off into 
the air. These spores are carried away by the wind and may 
find lodgment on the leaves, twigs or fruit of the proper alternate 
host. Under favorable conditions of moisture, the basidiospores 
germinate and the tissue of the pomaceous host is penetrated 
and a new growth of mycelium started. The area of tissue 

invaded is limited 
to a small spot 
which becomes 
somewhat swollen 
and light yellow in 
color (Fig. 29). A 
short time after 
these symptoms 
become apparent, 
long whitish tubes 
of fungous tissue 
are pushed out all 
over the affected 
areas (Fig. 30). 
These tubes some- 
times split and 
form a fringe 
around cup-like depressions in the leaf, twig or fruit, in which 
are formed powdery masses of yellow spores (seciospores). 
These dust out, are borne by the wind and may continue the 
life history of the fungus if they lodge on the leaves or twigs 
of the proper species of juniper or cedar. 

These rust-fungi are important because they deform the tree 
when galls, witches'-brooms or cedar-apples are formed in abun- 
dance. The tissues of the affected branches die eventually and 
leave dead areas where wood-rot fungi may enter. On the 
apple-like hosts, which include not only many important cul- 







4 




1 
* 


r ■■ 
1 ■ % 



Fig. 29. — Cedar-apple fungus on wild apple leaves. 



JUNIPER DISEASES 



195 



tivated fruits but also many valued ornamentals, much damage 
is caused by defoliation when infection is heavy. 

Control. 

The control of these fungi is simple if one or the other of the 
alternate hosts is eliminated. Although cases have been noted 
in which a sepa- 
ration of one to 
several miles did 
not totally pre- 
vent the exchange 
of spores, a dis- 
tance of one mile 
between the two 
required kinds of 
trees reduces the 
amount of infec- 
tion to a mini- 
mum. Spraying 
either the conifer 
or pomaceous 
host has not been 
successful. In 
some states where 
junipers are a 
menace to or- 
chards because of 
the rusts, laws are 
in force requiring the destruction of all specimens within 
one mile of orchards. 

Reference 

Kern, Frank Dunn. A biologic and taxonomie study of the genus 
Gymnosporanguim. Bui. N. Y. Bot. Gard. 7 : 391-483, pis. 151- 
161, figs. 1-36. 1911. 




Fig. 30. — Cedar-apple fungus on haw leaf. 



196 MANUAL OF TREE DISEASES 

Leaf- and Twig-Rusts 

Caused by species of Gymnosporangium 

A few species of the rust-fungi belonging to the genus Gym- 
nosporangium attack the green twigs and leaves of various juni- 
pers without causing any over-growth of the affected parts. 
The symptoms of these diseases are confined to the brown spore- 
masses developed either on the leaf or between the leaves. The 
life history of these forms is similar to the other species of the 
same genus and is discussed on page 192. Below are given the 
hosts and characteristics, in brief, of these diseases. 

In Colorado, Utah and New Mexico, the Utah juniper is at- 
tacked by G. inconsincimm Kern. A yellowing of the leaves 
on the affected twigs may be noticed and in early spring small 
brown cushion-like spore-masses, the size of a pin-head, are 
formed from between and around the margins of the appressed 
scale-like leaves. The alternate stage occurs on species of 
service-berry. 

In Colorado a similar appearing species, G. multiporiim Kern, 
attacks the Utah and one-seed juniper. The alternate hosts 
are not known. 

In Texas several species of juniper are attacked by G. exiguum 
Kern. Short brown conical spore-masses, a sixteenth of an inch 
long, are pushed out from the affected leaves. The alternate 
host is Cratwgus Tracyi. 

In northeastern and north central United States, Juniperus 
sihirica is attacked by G. Davi^sii Kern. Spore-masses appear 
as small brown pustules on the leaves or at the base of leaves on 
the twig. The alternate stage occurs on species of mountain ash. 

A foreign species, G. koreaen^e (P. Henn.) Jackson, recently 
has been found established in Oregon on an imported juniper, 
Juniperus chinensis. Spore-masses form on the leaves of the 
juniper. The alternate stage occurs on cultivated quince and 
introduced Asiatic species of quince and pear. 



JUNIPER DISEASES 



197 




Fig. 31. — Cedar-appbs, early 
stages of development. 



Cedar-Apples 

Caused by Gymnosporangium juniperi-virginiance Sehw. and 
G. globosum Farlow 

The two diseases of the red 

Juniper known as cedar-apples or 

cedar-flowers are similar in nature 

and are found commonly in eastern 

and central United States. The 

first pathogene mentioned above 

has its alternate stage on the culti- 
vated apple and other species of 

Malus, while the latter pathogene 

occurs on various species of haw, 

mountain ash and the cultivated 

apple, and pear. The junipers 

are often covered with hundreds of the brown, globose galls 

which spoil the appearance of 
ornamental trees and result in 
more or less damage to the twigs 
and general vigor of the tree. The 
two pathogenes are the cause of ap- 
ple and pear rust respectively and 
cause seripus losses in yield when 
they cause defoliation. Climatic 
conditions and the proximity and 
abundance of the two kinds of hosts 
in the same locality are the deter- 
mining factors which influence the 
severity of these diseases on both 
hosts. 

Symptoms. 
„ „„ „ , , ■ , ^ Brown-colored bodies called 

l IG. ^2. — Cedar-apple in late 

autumn, one year after infection. Ccdar-apples or Cedar-flowcrS are 




198 



MANUAL OF TREE DISEASES 



produced on the small twigs of the red juniper. When very 
young, the galls can be seen to start as outgrowths of the juniper 
leaves (Fig. 31). The tissues of the leaf are stimulated to over- 
growth and finally form, in a single season, the large cedar- 
apples, which are often an inch in diameter (Fig. 32). In this 




Fig. 



33. — Cedar-apple in spring of second year, 
showing expanded spore-horns. 



condition they pass the winter, and the following spring brown 
horns of spores are pushed out from the surface of the cedar- 
apples (Fig. 33). In the former species these horns are about 
one inch long and cylindrical, while in the latter fungus they 
are about one-half inch long and are flattened or wedge-shaped. 



JUNIPER DISEASES 199 

Cause. 

Cedar-apples on juniper are caused by two different species 
of the rust-fungi, Gymnosporangium juniperi-virgmiance and 
G. glohosum. The hfe history of these fungi is described on page 
192 in the general discussion of several species of the same genus. 
In the case of the two cedar-apple rusts, the leaves of the juniper 
are infected by seciospores formed on the apple, pear, haw or 
other pomaceous host. This takes place during midsummer or 
in the fall and no symptoms on the juniper are apparent until 
late spring of the next season. At that time the infected leaf 
shows a small greenish outgrowth, and in the summer from this 
small beginning the large cedar-apple develops (Fig. 32). The 
tissue inside the gall is made up of a mixture of large host-cells 
and intercellular mycelium. The outer layers of the gall are 
corky and reddish or chocolate-brown. Scattered over the sur- 
face, in late autumn, are numerous depressions from each of 
which a bundle of hyphae grow out the following spring and 
form the horns covered with teliospores. 

References 

Hesler, L. R., and Whetzel, H. H. Manual of fruit diseases, pp. 63- 

71, 341-344, figs. 17-19, 94. 1917. 
Weimer, J. L. Three cedar rust fungi, ttieir life histories and the 

diseases they produce. Cornell Univ. Agr. Exp. Sta. Bui. 390 : 

507-549, figs. 136-157. 1917. 
Heald, F. D. The life history of the cedar rust fungus Gj-mno- 

sporangium Juniperi-^nrginianEB Schw. Nebraska Agr. Exp. Sta. 

Ann. Rept. 22: 105-113, pis. 1-13. 1909. 
Reed, H. S., and Crabill, C. H. The cedar rust disease of apples caused 

by Gymnosporangium Juniperi-virginianns Schw. Virginia Agr. 

Exp. Sta. Tech. Bui. 9 : 3-106, figs.^ 1-23. 1915. 
Giddings, N. J., and Berg, A. Apple rust. West Virginia Agr. Exp. 

Sta. Bui. 154 : 5-73, pis. 1-10. 1915. 
Coons, G. H. Some investigations of the cedar rust fungus. Nebraska 

Agr. Exp. Sta. Ann. Rept. 25 : 217-246. 1912. 
Pammel, L. H. The cedar apple fungi and apple rust in Iowa. Iowa 

Agr. Exp. Sta. Bui. 84: 1-36, figs. 1-11. 1905. 



200 MANUAL OF TREE DISEASES 

Rust Witches'-Brooms 

Caused by Gymnosporangium Nidus-avis Thaxter, G. juvenescens Kern 
and G. Kernianum Bethel 

Three witches '-broom diseases are caused by species of 
rust-fungi on different junipers. The first species mentioned 
above causes witches'-brooms of the red juniper in eastern and 
central United States. The brooms are simply tufts of many 
branches which are formed from the part of the parent branch 
affected by the rust-fungus. The leaves of the brooms are usu- 
ally of the pointed, awl-shaped, juvenile tj^e. The second 
species causes large brooms on the red and Rocky Mountain 
juniper in the Rocky Mountains and in northwestern and north 
central United States. The leaves of these brooms also are of 
the juvenile type. The third species causes globose, compact 
brooms on the Utah juniper in western Colorado. The leaves 
on the brooms on this tree are scale-like. 

The life history of all three species is similar to the other rusts 
of this type occurring on junipers and is discussed on page 192. 
The spore-masses in the first species appear as linear cushion-like 
brown masses bursting the bark of the affected branches, while 
in the other two species they are small hemispherical brown 
bodies, the size of a pin-head or smaller and arise from between 
the leaves or in the leaf-axils. Various species of service-berry 
are the alternate hosts for these three species. The first species 
is known to infect the quince also. 

Branch-Galls 

Caused by several species of Gymnosporangium 

Abrupt swellings of the stems of the various species of juniper 
are often caused by species of the rust-fungi belonging to the 
genus Gymnosporangium. Other species of the same group of 
rusts cause cedar-apples and long fusiform branch-swellings, 



JUNIPER DISEASES 201 

and a few produce spore-cushions on the normal green twigs and 
scale-Hke leaves. The life history of these fungi is described on 
page 192. The main characteristics of the forms causing abrupt 
swellings are given below. 

The red juniper is affected in southeastern and south central 
United States by GyiiiJiosporangium trachysoriim Kern. Small 
knots or galls as large as an inch in diameter and an inch and a 
half long are formed on the small branches. The spore-horns are 
pushed out from these galls and are wedge-shaped and less than 
a half inch long. The alternate stage occurs on species of haw. 

In the same region the red juniper is attacked by Gyvmospo- 
rangium floriforme Thaxter. Small gall-like excrescences as 
large as one-half inch across and occasionally globose swellings 
an inch in diameter are formed on the branches. The horns of 
spores are cylindrical and pointed and vary from an eighth to 
one-half inch in length. One species of haw {Cratcegus spathu- 
lata) is known to be the alternate host for this rust. 

Along the coast of the Gulf of ]\Iexico from Mississippi to 
Florida, several species of juniper often show reddish brown 
globose galls, a quarter to one-half inch in diameter. The fungus 
causing this gall is Gymnosporangium bermudianum (Farlow) 
Earle. This species is peculiar and is different from all others 
of this group in that no alternate host is required for its develop- 
ment. Both the teliospores and seciospores are formed on the 
same galls on the juniper. The cluster-cup stage is followed 
by teliospore masses smaller than a pin-head. 

In northwestern United States and adjacent Canada, the 
dwarf juniper and Juniperus sihirica are attacked by Gymnospo- 
rangium jumperinum (L.) IVIart. Hemispherical swellings half 
an inch to two inches long are formed on the larger branches 
and more or less globose galls an inch in diameter appear on 
the smaller branches. The spore-masses are flat and cover large 
areas of the galls. The alternate hosts are species of mountain 
ash. 



202 MANUAL OF TREE DISEASES 

In the same region as above, the Rocky Mountain juniper is 
attacked by Gymnosporangimn Betheli Kern. Irregular gall- 
like knots are produced which are two or three times the 
diameter of the normal branch. Several knots breaking out ad- 
jacent to each other form galls similar to the black knots com- 
mon on plum and cherry. Short wedge-shaped spore-horns 
about an eighth of an inch long are pushed out from the bark of 
the galls. Several species of haw are known to be the alternate 
hosts for this rust. 

In northwestern and southwestern United States, the Rocky 
Mountain, Utah and one-seed junipers are attacked by Gym- 
nosyorangium Nelsoni Arthur. Hard woody globose galls as 
large as two and one-half inches are formed. The spore-masses 
are flattened and about an eighth of an inch high. The alter- 
nate hosts of this species are the quince, pear and species of 
service-berry. 

The red juniper in northeastern and north central United 
States is attacked by Gymnosporangium corniculans Kern. 
Irregularly lobed excrescences as large as an inch in diameter 
are produced. The spore-horns are conical and about one- 
eighth of an inch high. The alternate hosts are species of serv- 
ice-berry. 

Fusiform Branch-Swellings 

Caused by species of Gymnosporangium 

In addition to cedar-apples and galls or knots, several species 
of the rust-fungi cause long spindle-shaped swellings of the 
branches of species of juniper. The life history of these fungi 
is discussed on page 192 and only the hosts and outstanding 
characteristics of the diseases are given below. 

In eastern, southeastern and central United States, the red 
and dwarf juniper and J. sihirica are commonly affected by 
Gymnosporangium germinale (Schw.) Kern. The branches are 
slightly enlarged, often for several inches in length. The spore- 



JUNIPER DISEASES 203 

masses break through the bark as orange-yellow hemispherical 
pustules about an eighth of an inch high. The alternate hosts 
are quince, apple and species of service-berry and haw. 

In northeastern United States and westward to Wyoming and 
Colorado, the dwarf juniper, and Jimiperus sibirica are affected 
by Gymnosporangium clavariaforme (Jacq.) DC. The branches 
of all sizes are attacked and slightly swollen for several inches. 
Spore-horns are produced in abundance in the spring from 
the swellings. They are brownish yellow and about one-half 
inch long. The alternate stage of this rust is produced on 
quince and species of service-berry. 

Along the Atlantic Coast the red juniper is attacked by Gym- 
nosporangium effusum Kern. Long slender enlargements of 
the smaller branches less than an inch in diameter are pro- 
duced. This fungus also causes swellings on the trunks. 
The spore-masses are wedge-shaped and often as large as one- 
half inch high by a quarter of an inch long at the base. The 
alternate host for this species is unknown. 

Several species of juniper in Colorado, New Mexico and Ari- 
zona are attacked by Gymnosporangium gracilens (Peck) Kern 
and Bethel. Long spindle-shaped swellings of the branches are 
formed. The spore-masses break through the bark in long rows 
and are about an eighth of an inch high. Species of Fendlera 
and Philadelphus are alternate hosts of this rust. 

In the region extending from northeastern United States to 
Colorado and Wyoming, the red juniper and Juniperus sibirica 
are attacked by Gymnosporangium cornutum (Pers.) Arthur. 
The smaller woody branches are slightly enlarged. The spore- 
masses are flat or cushion-like and not extensive. Mountain 
ash is the alternate host. 

In a restricted region in Kentucky and Missouri, the red 
juniper is attacked by Gymnosporangium exterum Arthur and 
Kern. Short spindle-shaped swellings are produced and the spore- 
masses in the spring are fiat and anastomosing. The alternate 



204 MANUAL OF TREE DISEASES 

host for this species is Porteranthus {Gillenia) stipulatus (Muhl.) 
Britton. 

White Bark 

Caused by Cyanospora albicedrce Heald and Wolf 

This disease is common on the mountain juniper throughout 
its range in Texas. White patches, either small or extensive, 
occur on the bark of the young twigs and larger branches of 
young trees. The twigs are killed after the white areas have 
encircled them. Many of the branches, or the entire tree, may 
be killed in this manner. Shading seems to make the twigs and 
branches more susceptible. Upon the whitened areas of the 
bark numerous grayish pustules are formed, containing the 
fruiting-bodies of the fungus. After the bark is decayed, the 
pustules stand out prominently. Projecting from the upper 
surface of the grayish pustules are one to three short beaks which 
represent the openings of the fruiting-bodies buried in the pus- 
tules. Ascospores are formed in these fruiting-bodies and ooze 
out through the openings during moist weather. 

Reference 

Heald, F. D., and Wolf, F. A. The whitening of the mountain cedar, 
Sabina sabinoides (H. B. K.) Small. Mycologia 2:205-212, 
pi. 31, figs. 1-3. 1910. 

Brown Pocket Heartwood-Rot 

Caused by Fomes roseus Fries 

This heartwood-rot was first described as a disease of juniper, 
but recently has been found commonly in fir, larch, spruce, pine, 
hemlock and occasionally in arbor-vitse, birch and maple, over 
practically the entire United States wherever conifers are im- 
portant forest-trees. It may be confused in some trees with the 
red-brown root- and butt-rot caused by Polyporus Schtveinitzii (see 
page 294), unless the fruiting-bodies are present to identify it. 



JUNIPER DISEASES 



205 



Symptoms. 

The wood of the juniper is characteristically affected. Long 
cylindrical and pointed pockets of brown charcoal-like decayed 
wood are formed. At first these pockets are more or less sepa- 
rated and vary from one to several feet in length. Later they 
may increase in diameter 
and merge with neighboring 
pockets, forming large irregu- 
lar decayed areas. The de- 
cayed wood in juniper is 
dark brown but in other 
trees may be lighter if the 
normal wood is light colored. 
It breaks into cubes and is 
easily powdered. With a 
knife blade the charcoal-like 
cubes may be scraped from 
the cavity, leaving it smooth. 
The wood around these cavi- 
ties is normal and of the 
natural color. 

The fruiting-bodies of the 
causal fungus on juniper are 
produced in the holes in the 
trunk where branch stubs are 
inclosed. They conform to 
the size and shape of the 
hole. When formed on logs, 
they vary from thin shelves to thick hoof-shaped rose- 
colored bodies which are usually small (Fig. 34). The 
upper surface may become black with age while the mar- 
gin and under surface of newly formed pores is pinkish 
red. The internal structure is flesh-colored or pinkish. 




\ : ■■' 



Fig. 34. — Fruiting-bodies of Fames 
roseus. 



206 MANUAL OF TREE DISEASES 

The pores in the under surface are minute and the tubes 
very short. 

Cause. 

The brown pocket-rot of conifers is caused by the fungus 
Fomes roseus (formerly called Polyyorus carneus Nees). The 
fruiting-bodies described above are perennial and are formed 
from dead areas on living trees or on the dead trees after they 
fall. Infection seems to take place mostly near the base of the 
tree and the rot is confined to the lower part of the trunk. The 
wood is destroyed in the pockets by the extraction of the cellu- 
lose. The lignin remains and the fibers retain their entirety, 
although the walls are much thinner than normal. For a fuller 
description of the life history and control of wood-rotting fungi, 
see page 64. 

References 

Sehrenk, Hermann von. Red rot, or pecky cedar (Polyporus carneus). 

In Two diseases of red cedar, caused by Polyporus juniperinus 

n. sp. and Polyporus carneus Nees. U. S. Dept. Agr. Div. Veg. 

Phys. and Path. Bui. 21 : 16-20, pis. ,5-7, fig. 3. 1900. 
Hedgcock, G. G. Notes on some diseases of trees in our national 

forests. IV. Phytopathology 4 : 181-188. 1914. 

White Pocket Heartwood-Rot 

Caused by Fomes juniperinus Sclirenk 

Junipers are affected by this destructive heartwood-rot in 
central United States. At times, the trees are made hollow 
for several feet up and down the trunk. Trees more than 
twenty-five years old are more often attacked than younger 
individuals. 

Symptoms. 

Varying with the stage to which the decay has progressed, the 
affected trees show one or more large holes at the center or are 



JUNIPER DISEASES 207 

hollow. At first the decayed areas are a few inches in length 
and pure white and are separated from one another by several 
inches of sound wood which appears normal except that it is 
somewhat brownish. Soon the white areas become holes with 
their inner surfaces lined with white fibers mixed with a reddish 
yellow felt of mycelium. The wood around the holes is brown- 
ish and shades off gradually to the deep red normal wood. The 
amount of soft white fibers around the edges of the large hole is 
considerable and very striking in appearance when compared 
with the normal red wood. When the holes become large, they 
often fuse and cause hollow trunks. In very large trees there 
may be several holes parallel to each other. 

The fruiting-bodies of the causal fungus are very rare and 
appear at branch wounds. They are woody and usually hoof- 
shaped. The upper surface is at first yellowish orange and later 
turns to black with a yellowish margin. When young the top 
is smooth but with age it becomes fissured. The lower surface 
is yellowish brown. The inner substance of the fruiting-body 
is reddish orange. A new layer of tubes is formed each year. 

Cause. 

White pocket heartwood-rot or white rot of junipers is caused 
by Fovies juniperinus. The fruiting-bodies described above 
are very rarely found. Infection is initiated by spores which 
lodge on a broken stub of a branch. The mycelium penetrates 
into the center of the heartwood of the trunk where the first evi- 
dence of decay is the turning white of the normally red wood. 
Later new areas of decay originate a few inches above and below. 
The lignin is abstracted from the cell-walls and the primary 
layers of the walls are dissolved. These two actions leave the 
remainder of the walls pure white and unattached to one an- 
other, so that they fall apart leaving a hole in the wood. The 
life history and control of the w^ood-rot fungi are more fully 
discussed on page 64. 



208 MANUAL OF TREE DISEASES 



References on White Pocket Heartwood-Rot 

Schrenk, Hermann von. White rot of the red cedar (Polyporus juni- 
perinus n. sp.). In Two diseases of red cedar, caused by Poly- 
porus juniperinus n. sp. and Polyporus carneus Nees. U. S. 
Dept. Agr. Div. Veg. Phys. and Path. Bui. 21 : 9-16, pis. 1-4, 
figs. 1-2. 1900. 

Hedgcoek, G. G., and Long, W. H. Preliminary notes on three rots 
of juniper. Mycologia 4: 109-114, pis. 64-65. 1912. 



Yellow Wood-Rot 

Caused by Forties Earlei (Murrill) Sacc. ( ? = Fomes juniperinus 

Schrenk) 

This wood-rot is similar in appearance to the white heartwood- 
rot of the red juniper. The yellow wood-rot occurs more or less 
commonly in Arizona, New Mexico, Texas and Colorado in 
mountain, one-seed and Utah juniper. The rot is most de- 
structive in New Mexico, and at times the tree is so weakened 
that it breaks over. 

Symptoms. 

Long longitudinal holes several inches in diameter are formed 
in the heartwood. The holes are partially filled with decayed 
wood matted together with light brown mycelium. The wood 
around the holes is yellowish or light brown in color. Both the 
heartwood and sapwood may be invaded and destroyed, al- 
though the holes are usually confined to the heartwood. 

The sporophores of the causal fungus are attached to the 
affected tree. They emerge from the furrows or depressions 
in the bark, usually within ten feet of the ground. They are 
hoof-shaped to cylindrical, woody bodies, brownish to black 
and deeply checked on top and yellowish beneath. The 
inner substance of the sporophore is brownish or orange- 
yellow. The pores on the under surface are rather large and 
circular. 



JUNIPER DISEASES 209 

Cause. 

The yellow wood-rot of the species of juniper found in the 
Southwest is caused by a fungus named Fomes Earlei. There 
is but little difference between this fungus and Fomes jun.i- 
periniis, causing the white pocket heartwood-rot of red juniper 
in eastern United States. Very few sporophores of Fomes 
juniperinus have been found, although the rot caused in red 
juniper is common. Sporophores of Fomes Earlei are common 
where the trees are affected. It is believed by some that the 
two species are identical but because very few specimens of 
Fomes juniperinus are available for comparison, this has not 
been fully determined. The rots are somewhat different al- 
though similar in many respects. These differences may be 
due, however, to the host and do not necessarily indicate that 
the fungi causing them are different species. Further details 
concerning the life history and control of wood-rot fungi will 
be found on page 64. 

Reference 

Hedgcock, G. G., and Long, W. H. Preliminary notes on three rots 
of juniper. - Mycologia 4 : 109-114, pis. 64-65. 1912. 

Stringy Brown Wood-Rot 

Caused by Fomes texanus (Murrill) Hedgcock and Long 

This wood-rot affects both the heartwood and sapwood of 
mountain, Utah and one-seed juniper. The rot is very destruc- 
tive and common in Texas and New Mexico. 

Symptoms. 

The first signs of the decay are evident as small pockets of 
light brown tissue in the spring-wood of the annual rings. 
These pockets soon merge and the spring-wood becomes reddish 
brown and is partially or entirely destroyed. This action leaves 
concentric zones of badly rotted and apparently sound wood 



210 MANUAL OF TREE DISEASES 

which is characteristic of this wood-rot. Hollow trunks are 
not formed. The less aflFected summer- wood of the rings and 
the wood bordering the decayed area are yellowish brown. The 
sapwood and bark are affected and permeated by the reddish 
yellow mycelium. 

The sporophores of the causal fungus appear from crevices in 
the bark where the fungus has emerged from the sapwood and 
inner bark. They are hoof-shaped or cylindrical woody bodies 
with a light yellowish or brown to black checked upper surface. 
The yearly growth of the sporophore is apparent in the concen- 
tric furrows on the upper surface. The under surface is light 
yellowish and the pores are very small. The inner structure is 
yellowish. 

Cause. 

The stringy brown wood-rot of junipers in the Southwest is 
caused by the fungus Fomes texanus. No definite studies are 
reported on the method of infection. The general life history 
and control of the wood-rot fungi are discussed on page 64. 

Reference 

Hedgeock, G. G., and Long, W. H. Preliminary notes on three rots 
of juniper. Myeologia 4: 109-114, pis. 64-65. 1912. 

Basal Heartwood-Rot 

Caused by Porta Weirii Murrill 

This heartwood-rot is the most important basal decay of the 
western red cedar throughout northwestern United States. 
After the tree falls, the heartwood and sapwood of the entire 
tree are soon destroyed by the same fungus. In the first stages 
of decay, the wood is uniformly split into its separate annual 
rings. The affected wood is brown and brittle. 

The causal fungus forms fruiting-bodies on the fallen trunks 
of the affected trees. These fruiting-bodies are brown and 



JUNIPER DISEASES 211 

rather soft sheets of fungous material spread over extensive 
areas on the sides and bottom of the log. A single fruiting-body 
may extend for several feet along the log. The surface of the 
fruiting-body is covered with very fine pores. Two or three 
layers of tubes may be found representing as many years of 
successive growth and spore production. 

Reference 

Murrill, W. A. An enemy of the western red cedar. Mycologia 
6 : 93-94, pi. 122. 1914. 



CHAPTER XXIII 

LARCH DISEASES 

The three native species of larch or Larix are important 
forest-trees in northeastern and northwestern United States. 
The eastern and European larch are frequently used as orna- 
mentals. The eastern larch is commonly affected by several 
wood- and root-rots. Of these, the pecky wood-rot and red- 
brown sapwood-rot are most destructive. The leaf-rusts are 
rare. In the Northwest, the larch is not only subject to sev- 
eral wood- and root-rots but is also seriously damaged by a 
dwarf mistletoe which causes large swellings and witches'- 
brooms. The seedlings are often killed by a fungus which 
causes a root-rot. 

Seedling Root-Rot 

Caused by Rhizina xmdulata Fries 

Seedlings of the western larch are killed by this root-rot 
in northwestern United States. It may be found also in some 
northeastern states since the fungus is known to occur in this 
region. The diseased roots of seedlings from three to six years 
old are matted together by an abundant growth of white my- 
celium. The fruiting-bodies of the pathogene are formed on 
the surface of the ground. They are dark brownish, undulat- 
ing structures with a light colored margin when young. A 
fuller description of this disease is given under hemlock diseases, 
page 177. 

Leaf-Rusts 

Caused by Melampsora Bigelowii Thiim. and M. Medusae Thum. 

The needles of larch are sometimes affected by two similar 
rusts. These diseases have been found in various localities 

212 



LARCH DISEASES 213 

and may be expected throughout the northern states from 
the Atlantic to the Pacific. The fungi causing these two dis- 
eases are closely related to the several other rust fungi of 
pine, spruce, fir and hemlock. 

Symptoms. 

The rusts of larch are so similar that they cannot be 
identified without the use of a microscope. The affected 
needles in early spring show small whitish pustules bursting 
through the epidermis. The epidermis of the leaf covering of 
the pustules breaks open and the spores within are blown 
away by the wind as a fine dust. The needles then turn yellow 
and may fall off. 

Cause. 

The rust diseases of larch are caused by Melampsora 
Bigelowii and M. Medusce. Besides the stage produced on 
the larch leaves, each of these fungi requires a period of growth 
on other kinds of plants. The spores (seciospores) from the 
pustules caused by the first mentioned species infect the leaves 
of several kinds of willows. In the latter named species 
the seciospores infect the leaves of certain poplars. On the 
willows and poplars other spores (urediniospores) are produced 
which continue the life history of the fungi. Over-wintering 
teliospores on these two hosts germinate in the spring and pro- 
duce basidiospores which infect the young leaves of the larch. 
These facts in the life history of the two rust fungi make it 
evident that the appearance of the diseases on the larch is de- 
pendent on the presence of poplars or willows in close proximity. 

A blister-rust of larch needles which also occurs rarely in 
this country is caused by Melampsoridium hetidoe (Schum) 
Arthur. This fungus attacks birch in the United States but 
the stage on larch does not seem to be common. It is known 
on both birch and larch in Europe. 



214 MANUAL OF TREE DISEASES 

Mistletoe Burl and Witches'-Broom 

Caused by Razoumofskya laricis Piper 

The mistletoe disease of larch is common and destructive 
in northwestern United States. It is especially abundant in 
open stands and causes but little damage in the dense forests. 
In moist and fertile areas, the larch attains full development 
and is only rarely deformed by the mistletoe. On the other 
hand in regions of light rainfall, variable temperature, low 
humidity, dry soil and especially in open stands, the growth of 
the mistletoe is favored and the tree suppressed. Measure- 
ments made of unaffected and badly infested trees show that 
the rate of growth of the larch may be reduced to one-half the 
normal. 

Symptoms. 

Young and old larches are affected. The seeds of the mistle- 
toe produce infection if they fall on the green twigs. Burls 
are produced in the trunk and larger branches due to the irri- 
tation caused by the roots of the mistletoe. Infected younger 
branches are stimulated to produce abnormal twigs, forming 
witches'-brooms. The foliage area of the tree is reduced by 
the deforming of the branches and the general development 
of the tree is suppressed. 

Cause. 

This burl and witches'-broom disease is caused by one of 
the species of dwarf mistletoe, Razoumofshya laricis. The 
roots of the parasite penetrate the bark and wood and grow 
down the branch for some distance, sometimes entering larger 
branches or the trunk. The irritation caused by the roots 
of the parasite results in an increased growth of the affected 
parts. The parasitic plants are inconspicuous, never being 
more than about four inches tall. A cluster of yellowish 



LARCH DISEASES ■ 215 

leafless stems growing out from the bark is all that can be seen. 
A general discussion of mistletoe diseases will be found on page 
54. 

References 

Weir, J. R. Larch mistletoe : some economic considerations of its 
injurious effects. U. S. Dept. Agr. Bui. 317 : 1-25, figs. 1-13. 
1916. 

Weir, J. R. Mistletoe injury to conifers in the northwest. U. S. Dept. 
Agr. Bui. 360 : 1-38, pis. 1-4, figs. 1-27. 1916. 

Pecky Wood-Rot 

Caused by Trametes pini Fries 

Red-rot, ring-shake, peckiness or pecky wood-rot is the 
most destructive wood-rot of conifers in the United States. 
It is common in larch. The characteristics of the rot in larch 
are similar to those produced in spruce, with the exception that 
the action in the formation of pockets is less localized. The 
spring-wood of the affected annual rings is largely destroyed, 
leaving the denser summer-wood partially decayed and red 
in color. Black lines are formed at irregular places. The 
wood of the larch is thus more completely destroyed than that 
of the other conifers. The sapwood and bark are readily in- 
vaded and the living tissues killed, thus causing the death of 
the parts of the tree above, as in the spruce and fir. A 
more complete description of this wood-rot is given under 
spruce diseases, page 324. 

Red-Brown Sapwood-Rot 

Caused by Forties pinicola Fries 

Larch wherever it grows is commonly affected by this wood- 
rot. Spruce, pine, fir and hemlock are also affected. The 
wood is reduced to a red-brown powdery mass held together 
by numerous plates of whitish mycelium. The sporophores 



216 MANUAL OF TREE DISEASES 

of the causal fungus are formed abundantly on the diseased 
trees and on fallen logs. They have a red varnished margin 
and a cream-colored under surface. Fuller details concerning 
this heartwood-rot will be found under fir diseases, page 165. 

Brown Heartwood-Rot 

Caused by Fomes officinalis Fries ( = Fomes laricis (Jacq.) Murrill) 

This brown heartwood-rot is common and very destructive 
in western United States in larch, pine, Douglas fir and other 
conifers. In California and Nevada, sugar pines are the most 
destructively attacked. In the Northwest, Douglas fir, western 
larch, lodge-pole and western yellow pine are often seriously 
affected. The rot resembles to some extent the brown checked 
wood-rot caused by Polyporus sidpJmreus (see page 247). 

Symptoms. 

The affected heartwood is brownish or red-brown in color. 
Felts of the mycelium of the fungus form in cracks in the wood. 
The sporophores of the causal fungus are not formed abun- 
dantly on the affected trees. They are large hoof-shaped or 
globose bodies with a white, roughened, chalky upper surface. 
The white material will rub off like powdered chalk. The 
fruiting-bodies when young are soft and watery but become 
very brittle when old. The inner structure is white, bitter to 
the taste and has a distinct mealy odor. The under surface is 
convex, whitish and covered with small pores. 

Cause. 

The brown heartwood-rot of conifers in the western forests 
is caused by Fomes officinalis. This fungus also is known by 
the name Fomes laricis. Infection takes place when the spores 
from the tubes on the under side of the fruiting-body lodge in 
open wounds where heartwood is exposed. For further detail 



LARCH DISEASES 217 

concerning the general life history and control of the wood- 
rotting fungi, see page 64. 

Reference 

Meinecke, E. P. Forest tree diseases common in California and 
Nevada. U. S. Dept. Agr. Forest Service. Unnumbered pub- 
lication, pp. 1-67, pis. 1-24. 1914. 

Brown Pocket Heartwood-Rot 

Caused by Fomes roseus Fries 

This heartwood-rot is common in larch as well as in fir, spruce, 
pine and hemlock, in almost every section of the country where 
these trees grow. The rot may be confused at times with the 
red-brown root- and butt-rot caused by Polyjponis Schweinitzii 
(see page 294). The decayed wood is brown, easily powdered 
and looks like charcoal. At first long cylindrical or pointed 
pockets of decayed wood are formed. Later these pockets 
may join and large areas of the heartwood are uniformly brown 
rotted. The fruiting-bodies of the causal fungus are produced 
at branch stubs on affected trees or on the sides of fallen timber. 
They may be either small and thin structures or large hoof- 
shaped bodies. The under surface is rose-colored. For further 
details concerning this heartwood-rot, see under juniper diseases, 
page 204. 

Red-Brown Root- and Butt-Rot 

Caused by Polyporus Schweinitzii Fries 

Fir, pine, spruce, hemlock and arbor-vitse in addition to. 
the larch are affected by this wood-rot wherever these kinds of 
trees grow. It is next in importance to the pecky wood-rot 
of these trees. The affected heartwood of the roots and lower 
part of the trunk is at first yellowish and cheesy but later be- 
comes red-brown and brittle. This wood-rot is more fully 
described under pine diseases, page 294. 



218 MANUAL OF TREE DISEASES 

Yellow Root-Rot 

Caused by Sparassis radicata Weir 

In the Northwest the roots of larch are often destroyed by 
this root-rot. Fir, spruce and pine are affected by the same 
disease. The bark and sapwood of the roots- are killed. Yel- 
lowish fan-shaped plates of mycelium are found in the bark. 
The medullary-rays and heartwood are also decayed and be- 
come yellow or brown. The fruiting-bodies of the causal 
fungus are peculiar. They are attached to the diseased roots 
by long, fleshy stalks. New fruiting-bodies are formed each 
year from the tip of the stalk. They are large, white, compact, 
fleshy structures covered with curled and lacerated leaf-like 
plates. These thin plates stand upright on the upper portion 
of the fruiting-body or horizontally from the sides. The spores 
of this fungus are borne over the entire exposed surface of the 
fruiting-body. For further details concerning this root-rot, 
see under fir diseases, page 170. 



CHAPTER XXIV 

LOCUST DISEASES 

The native species of locust are unimportant forest-trees. 
The common locust of eastern United States {Robinia Pseuda- 
cacia) was more frequently used as an ornamental in previous 
years than at present. Insect damage has made the tree 
difficult to grow. The only fungous diseases of the locust that 
have considerable importance are the yellow and brown checked 
wood-rots. The yellow wood-rot is caused by a fungus that 
grows only in the wood of the locust. This rot is common in 
ornamental trees and often causes their death. 

Yellow Wood-Rot 

Caused by Fomes rimosus Berkeley 

The yellow wood-rot of the trunk and branches of the locust 
is common throughout the range of this tree. Young trees 
less than six inches in diameter are rarely affected. 

Symptoms. 

The central portion of the heartwood is reduced to a soft 
yellow spongy mass for several feet up and down the trunk or 
limb. From this central decayed area, as seen in cross-section, 
several V-shaped bands reach out radially toward the sapwood. 
When the wood is split lengthwise, these bands of decay are 
seen to be one or two inches wide. At the center of each band 
is a small reddish core and extending upward and downward 
from this core the partially decayed wood varies from orange- 

219 



220 



MANUAL OF TREE DISEASES 



yellow to light straw-yellow at the edge of the band. When 
the bands have reached the cambium and bark, compact red- 
brown felts of mycelium replace the destroyed tissues. In 
tangential section the narrow bands show as yellow lens-shaped 
areas with red centers. The radial bands of decay become 
more numerous and finally coalesce, and in this way all the 
heartwood and sapwood is decayed. 

The sporophores of the pathogene appear at various places 
on the bark where the mycelium has penetrated the sapwood 




Fig. 35. — Upper surface of fruiting-body of Fornes rimosus. 



and bark. They are at first small, red-brown, hard knobs. 
Each year a new layer of pores is added to the under surface. 
After several years' growth large brackets or hoof-shaped bodies 
are formed. The upper surface is dark brown or black and 
much roughened by numerous fissures which divide the surface 
into irregular squares (Fig. 35). The under surface is dull 
red-brown and extends upward over the edge of the sporophore 



LOCUST DISEASES 221 

in a smooth roll. The pores on the under surface are barely 
visible. 

Cause. 

The yellow wood-rot of locust is caused by the fungus Fomes 
rimosus. It is similar in appearance to Fomes igniarius except 
when it is broken open the older layers of tubes do not show 
the white filling. The spores from the tubes on the under 
surface of the sporophore infect the locust at branch stubs or 
through the tunnels made by the locust borer. The mycelium, 
after destroying the central portion of the heartwood, reaches 
out along the medullary -rays and initiates the bands of decay. 
The yellow wood-rot fungus is not known to continue growing 
in dead wood and timber made from affected wood is said to 
last as long as sound timber. For further details concerning 
the life history and control of wood-rotting fungi, see page 64. 

References 

Schrenk, Hermann von. A disease of the black locust (Robinia 

pseudacacia L.). Missouri Bot. Gard. Ann. Rept. 12:21-31, 

pis. 1-3. 1901. 
Schrenk, Hermann von, and Spaulding, P. Black locust disease 

caused by Fomes rimosus. In Diseases of deciduous forest trees. 

U. S. Dept. Agr. Bur. PL Ind. Bui. 149 : 45^6. 1909. 

Brown Checked Wood-Rot 

Caused by Polyporus sulphur eus Fries 

The heartwood and sapwood of locust is often reduced to a 
red powdery mass by the sulfur fungus. Oak, chestnut, walnut, 
butternut, maple and alder are the other principal kinds of 
trees commonly affected by the same rot. The sapwood and 
bark may be invaded and the tops of the trees or large limbs 
are thus killed. The sulfur-yellow and orange-colored fruiting- 
bodies of the causal fungus are produced in late summer from 
wounds or from the bark where the mycelium has in^'aded the 



222 MANUAL OF TREE DISEASES 

sapwood. The reddish colored decayed wood spHts into small 
cubes with plate-like sheets of mycelium filling up the cracks 
between. This wood-rot is similar in its effect on the different 
kinds of trees and is more fully described under oak diseases, 
page 247. 

Root-Tubercles 

Caused by Bacillus radicicola Beijerinck 

Locust roots often show small globose swellings. These 
structures are abnormal lateral rootlets which are inhabited 
by the nitrogen-fixing bacterium. The bacteria gain entrance 
to the root through the root-hairs. They multiply in the cortex 
cells and stimulate the tissues to over-growth. A discussion 
of the relation between the host and parasite will be found 
under alder diseases, on page 88. 



CHAPTER XXV 
MAPLE DISEASES 

Many species of maple occur in all parts of the United States, 
They are important forest-trees in the eastern and central states. 
Several of the native and a few exotic species are the most 
widely used of any trees for shade and ornament. The maples 
are of the genus Acer (including Negundo). 

In the forest the maple is seriously affected by the common 
white wood-rot. Other wood-rots are also occasionally found. 
Outside the forest, maples are subject to» many diseases which 
at times are important. Several species of fungi cause diseases 
of the leaves which may result in defoliation (see page 30). 
Maples are also commonly affected by sun-scorch (see page 22). 
The wilt disease has not been thoroughly investigated but is 
known to have caused the rapid death of trees in several iso- 
lated places. These diseases, together with the several wood- 
rots, account to some degree for the commonly noted poor 
condition of maples. 

Tar Leaf-Spot 

Caused by Rhytisma acerinum Fries 

The large tar-like blotches on maple foliage are very con- 
spicuous. The leaves which develop several spots are often 
shed prematurely, and young nursery trees may suffer per- 
manent injury from defoliation. In eastern United States 
the red and silver maple are often attacked. In Europe the 
Norway and Sycamore maple are commonly affected by the 
same disease. In this country the Norway and Sycamore 

223 



224 



MANUAL OF TREE DISEASES 



maple are rarely if ever affected, even when growing among 
red and silver maples which are severely infected. This sub- 
stantiates the results of investigations in Europe which show 
that there are various strains of the tar-spot fungus. These 
strains show preference for certain species of maples, but in 
other respects are indistinguishable from one another. 

Sym2)toms. 

The first evidence of the developing spots on the maple leaves 
are light green or yellowish areas. In the summer the spots 
become black on the upper surface of the leaf due to the 
black mycelium of the fungus. The surface of the tar-like 

spots is wrinkled 
with anastomos- 
ing furrows and 
somewhat raised 
above the surface 
of the leaf. The 
spots are usually 
a quarter or half 
inch across (Fig. 
3G). 

Cause. 

The tar leaf- 
spot of maples is 
caused by the 
fungus Rhytisma 
acerinum. Spores are borne free on the upper surface of the 
black mass of fungous tissue as it develops on the leaf. It is 
not known whether these spores infect other leaves or not. 
But from the number of leaves affected on some trees, it 
seems certain that these spores must account for the general 
prevalence of the infections. When the spotted leaves fall 




Fig. 36. — Tar leaf-spot of maple. 



MAPLE DISEASES 225 

to the ground, the mycelium inside the black spots develops 
ascospores. These are mature in the spring. With the return 
of warm weather, the black layer of fungous tissue cracks 
open and the edges fold back, exposing the fruiting-layers 
within. The spores are probably shot into the air as are most 
ascospores. The young maple leaves are infected by the 
ascospores which lodge upon them and germinate. 

Control. 

Very little trouble will be experienced from this disease if 
the affected leaves are destroyed by burning in the autumn. 
Unless this is carefully done and all the affected leaves under 
and around the trees are destroyed, the few remaining ones 
may cause some infection in the spring. In exceptional cases, 
as in nurseries, spraying with bordeaux mixture as the leaves 
develop may be desirable. For general directions on spraying, 

see page 357. 

References 

Stewart, F. C. Black spot, Rhytisma acerinum (Pers.) Fr. In 

Notes on New York plant diseases, 1. New York Agr. Exp. 

Sta. (Geneva) Bui. 328 : 364. 1910. 
Schrenk, Hermann von, and Spaulding, P. Tar-spot. In Diseases of 

deciduous forest trees. JJ. S. Dept. Agr. Bur. PI. Ind. Bui. 

149 : 19. 1909. 

Black-Specked Leaf-Spot 

Caused by Rhytisma punctatum Fries 

The silver maple of eastern United States (Acer saccharinum) 
and the broad-leaf maple {A. macrophyUimi) of the Pacific 
Coast are occasionally affected by this leaf-spot. It does not 
seem to be as abundant as the tar leaf-spot. During the 
summer light green or yellowish areas about a half inch in 
diameter appear in the leaf. Later several isolated black 
spots the size of a pin-head develop on the upper surface of 
the spot. In the autumn the affected area remains yellowish 



226 



MANUAL OF TREE DISEASES 



green after the remainder of the leaf has faded or turned 
bright colored. The fungus causing this leaf-spot is a near rela- 
tive of the tar leaf-spot fungus (see page 223) . Spores are de- 
veloped in the same manner and control measures are the same 
for both diseases. 

Leaf-Spots 

Caused by Phyllosticta minima (B. and C.) E. and E., Gloeosporium 
apocrypturn E. and E., and other fungi 

The leaves of maple are subject to a number of leaf-spot 
diseases (see page 30). The two fungi named above are com- 
mon in eastern United States and may be found every year. 





Fig. 37. — Leaf-spot of maple caused by Phyllosticta minima. 



MAPLE DISEASES 



227 



In wet seasons defoliation may result. The illustrations show 
the effect of these diseases on the leaf (Figs. 37 and 38). Many 
of the other leaf-spots of maple appear similar to these, however, 
and no accurate 
determination can 
be made without 
a microscopic ex- 
amination of the 
fungus. 

The leaf-spot 
caused by Phyllo- 
sticta minima is 
characterized by 
light brown cir- 
cular spots with 
numerous black 
dot-like fruiting- 
bodies near the 
center (Fig. 37). 
The general char- 
acters of leaf- 
spots, and the life history of the fungi causing them, are more 
fully discussed on page 27. 




Fig. 



38. — Leaf-spot of maple caused by Gloeosporium 
apocryptuni. 



Powdery Mildews 

Caused by Uncinula circinata Cooke and Peek and Phyllactinia 
corylca (Pers.) Karst. 

Two species of the powdery mildew fungi are known on 
maple leaves in the United States, Uncinula circinata and 
Phyllactinia corylea (see page 35). The former has been 
reported from northeastern and central United States and 
the latter, which occurs on all kinds of trees, is distributed 
throughout the country. These two diseases cannot be dis- 



228 MANUAL OF TREE DISEASES 

tinguished from one another except by the microscopic char- 
acters of the black fruiting-bodies which are just visible to the 
unaided eye. The mycelium of both fungi causes powdery 
white, more or less definite spots on the under sides of the 
leaves. The life histories and control of powdery mildew fungi 
are discussed on page 37. 

Leaf-Blight 

Caused by Glceosporium sp. 

This leaf-blight has been observed on Norway maple {Acer 
platanoides) in Connecticut, New York and Virginia. No 
studies have been made on the disease and but little is known 




Fig. 39. — Leaf-blight of maple caused by GlcBosporium sp. 

concerning it. The leaves show yellowish and brown dead 
areas along the main veins (Fig. 39). Later the leaves wilt 
and fall from the tree. Minute brown spots form along the 
veins. These are the fruiting-bodies (acervuli) of the causal 



MAPLE DISEASES 



229 



fungus. The spores from these structures are disseminated by 
the rain. It is to be expected that perithecia with ascospores 
are formed in the leaves on the ground during the winter. 
The twigs have not been found affected. This disease is 
similar to the leaf- and twig-blight ^^^^^^^^^, ., 
of sycamores described on page 333. ^^^^^^^^«s^' * 
The control measures are the same 
for both of these diseases. 

Canker 

Caused by Nectria cinnabarina Fries 

Maples are commonly affected by 
this canker. Other deciduous trees 
may also be attacked by this disease 
but it never assumes great impor- 
tance owing to the causal fungus being 
only weakly parasitic. Twigs, small 
branches and young trees may be 
killed by the girdling action of the 
fungus. 

Symjitoms. 

Small depressed dead areas of bark 
around wounds or branch stubs are 
the first evidences of the developing 
canker (Fig. 40). Flesh-colored or Fio. 40. 
pink hemispherical bodies are pro- 
duced on the dead bark. Later the same pustules become 
chocolate-brown. If the fungus continues to spread, rolls of 
callus are formed around the affected area each year, until an 
open canker is produced which may girdle the limb. The 
mycelium grows most luxuriantly in the sapwood, causing a 
dark greenish discoloration (Fig. 41). The bark adjacent to the 




■ Nectria canker un 
maple. 



230 



MANUAL OF TREE DISEASES 



affected sapwood dies and the mycelium invades the dead bark, 
forming its fruiting-bodies on the outside. The canker develops 

slowly and may at any time cease 
to enlarge. The exposed wood is 
then finally overgrown by the callus. 
This canker is especially common 
in severely wounded or recently 
pruned trees. 

Cause. 

The canker of maples is caused 
by the fungus Nectria cinnaharina. 
Spores are borne over the outside of 
the flesh-colored pustules during the 
summer. After the pustules be- 
come chocolate-brown, perithecia 
are formed which produce asco- 
spores. These spores are matured 
over winter and produce infection 
in wounds in the spring. 

Control. 

The cankers can be removed by 
surgery (see page 351). All dead 
bark and twigs should be cut away 
at the same time, since the causal 
fungus occurs everywhere as a com- 
mon saprophyte. Pruning wounds should be at once protected 
by a wound dressing (see page 348). 




Fig. 41. — -Cross and longitudi- 
nal sections through a Nectria 
canker on maple. 



Reference 

Schrenk, Hermann von, and Spaulding, P. Nectria einnabarina. In 
Diseases of deciduous forest trees. U. S. Dept. Agr. Bur. PI. 
Ind. Bui. 149 : 21-22. 1909. 



MAPLE DISEASES 



231 



Wilt 
Caused by Vertieillium sp. 

Wilt is a recently discovered and little known disease of 
silver, Norway and sugar maples. It has been found in New 
York, Virginia and Ontario, Canada, and is probably more 
widely distributed. Several trees have been observed which 
were dying or had been killed by this disease. It seems 
probable that a part of the common sun-scorch of maples 
may be found to be another symptom of this disease. 

Symjitoms. 

In the few observations made on this disease, the common 
and only external symptom is the blanching and sudden wilt- 
ing of the foliage in midsum- 
mer. The leaves of an entire 
branch or side of the tree wilt 
and become dry and wrinkled 
at the same time. On cut- 
ting into the sapwood of the 
affected branch or trunk, the 
outer layers will be found more 
or less streaked with greenish 
colored longitudinal lines. No 
external fruiting-bodies have 
been found on the bark. The green discoloration extends up- 
ward and downward in the branches and trunk and may 
enter the roots (Fig. 42). 

Cause. 

The wilt of maples is due to an unnamed fungus of the genus 
Vertieillium. Closely related species cause a similar disease, 
usually confined to the roots, in barberry, eggplant and numer- 
ous other plants. Other species of the same genus cause wilts 




Fig. 42. — Sections through the trunk 
of a small maple affected by wilt. 



232 MANUAL OF TREE DISEASES 

of cotton, potato and various field crop plants. The fungus 
is known to form spores on branches of the mycelium but the 
manner and place of fruiting and method of infection in the 
maple is unknown. 

Control. 

Surgical methods are advised when this disease is to be con- 
trolled (see page 345). Several diseased trees in a group have 
been observed and the destruction of badly affected individuals 
is necessary to prevent the fungus spreading to healthy trees 
near by. 

Common White Wood-Rot 

Caused by Fomes igniarius Fries 

Silver and striped maple are more commonly aflFected by 
this white wood-rot than the red and sugar maple. Poplar, 
beech and oak are the most seriously affected of the many 
species of deciduous trees which are susceptible to this fungus. 
Beech and maple in mixture in the Adirondack Mountains are 
often diseased to the extent that the stands will never be worth 
cutting. Outside the forest, this disease is not so common. 
The sapwood may be invaded and the tops of the trees or 
large limbs killed. The sporophores and decay are similar for 
all kinds of trees and are described under poplar diseases, 
page 305. 

Brown Checked Wood-Rot 

Caused by Polyporus sulphureus Fries 

Maples are at times affected by the sulfur fungus which 
causes the brown checked wood-rot. Oak, chestnut, walnut, 
butternut, locust and alder are also frequently affected by 
the same rot. The wood is reduced to a reddish powdery mass 
which splits in cubes, separated by sheets of mycelium. The 
sporophores of the causal fungus are orange and sulfur-yellow 
in color. They form from branch wounds or directly from the 



MAPLE DISEASES 233 

bark In late summer. The sapwood and bark are often invaded 
and destroyed, causing the tops of the trees or large limbs to 
die. The symptoms of the brown checked wood-rot are simi- 
lar for all kinds of trees and are described under oak diseases, 
page 247. 

White Strand Wood-Rot 

Caused by Polyporus squamosus Fries 

Many kinds of deciduous trees are reported as seriously 
damaged by this white rot in Europe. Those specially men- 
tioned are. maple, oak, elm, walnut, basswood, willow, ash, 
birch, horse-chestnut and beech. In the United States, no 
•authentic information is available on this wood-rot, except 
that the fungus is found in some cases growing from wounds 
in living trees. 

Symjitoms. 

The heartwood and sometimes the sapwood of the trees are 
decayed. Trees in which the rot has affected the conduction 
tissue of the sapwood show marked decline and are often 
killed. The wood is characteristically rotted. It is almost 
white and marked with pure white narrow strands of mycelium 
running in the radial, tangential and longitudinal directions, 
causing the wood to be split into small cubes. In general this 
character is similar to the rot produced by Polyporus horealis 
in the wood of conifers (see page 185). 

The annual fruiting-bodies are easily recognized. They 
are soft and watery and almost circular with a short stout stem 
at one side attaching them to the tree. The top is slightly 
convex and is covered with overlapping brown scales, while 
the under surface is white and honeycombed. 

CmiM. 

The white strand wood-rot of maples is caused by the 
fungus Polyporus squamosus; so named because of the scales 



234 MANUAL OF TREE DISEASES 

on the top of the fruiting-bodies. It is commonly known as 
the scaly or saddle-back fungus. Infection is effected by the 
spores, which are wind-blown, lodging and germinating on 
exposed wood, especially at broken or pruned branch stubs. 
The less lignified elements of the wood-tissue are destroyed 
and strands of mycelium fill the long channels thus opened up 
in the wood. These strands run through the wood, replacing 
the medullary-rays and spring-wood, thus causing the white 
bordered cubes which are seen in cross and longitudinal sec- 
tions. The life history and control of the wood-rot fungi will 
be found discussed on page 64. 

References 

Schrenk, Hermann von, and Spaulding, P. White-rot caused by 

Polyporus squamosus. In Diseases of deciduous forest trees. 

U. S. Dept. Agr. Bur. PI. Ind. Bui. 149 : 48-49. 1909. 
BuUer, A. H. R. The biology of Polyporus squamosus, Huds., a 

timber destroying fungus. Jour. Econ. Biology. 1 : 101-138, 

pis. 5-9, figs. A-F. 1906. 

Uniform White Sapwood-Rot 

Caused by Hydnum sepientrionale Fries 

A white sapwood-rot of maple and beech is occasionally 
found in eastern and central United States. This rot has not 
been studied and described and is not very important. The 
affected wood is soft and uniformly white. Brown zones 
separate the affected area from the normal wood. Black 
lines are sometimes found running in various directions in the 
rotted wood. 

The white fruiting-bodies of the fungus are very conspicuous. 
They are large, flat, fleshy structures often a foot or two long 
and a foot across. They are composed of a thick sheet of 
mycelium adhering to the side of the tree with numerous 
closely overlapping projecting shelves. The individual shelves 



MAPLE DISEASES 



235 



are three or four inches long and project two or three inches 
from the tree. The under surface of the shelves is composed 
of pendent bristles or teeth (Fig. 43). The spores are borne 




- Lengthwise section through a f ruiting-body of 
Hydiium septentrionalc. 

over the surface of the teeth. The life history and control of 
the wood-rotting fungi are more fully discussed on page 64. 



White Streaked Sapwood-Rot 

Caused by Pleurotus osireatus Jaequ. 

Maples and other deciduous trees, such as basswood, elm 
and oak, are sometimes found affected by this sapwood-rot. 
Infection takes place in open wounds caused by various agents. 
The decayed area of wood is lighter 'n\ color than the normal 
wood and is bounded by a narrow brown zone. The medullary- 



236 MANUAL OF TREE DISEASES 

rays are destroyed and the porous portion of the annual rings 
is delignified and partially dissolved. The denser summer- 
wood of the rings is least affected. The result of this action 
is that the affected wood is light in weight and breaks easily 
into flakes. 

The sporophores of the causal fungus are fleshy, annual, 
shelving structures with radiating plates or gills on the under 
surface. The sporophores are more or less sessile and appear 
in clusters at wounds where the affected wood is exjDosed. 
They are often found at the junction between two limbs. The 
upper surface is smooth, slightly rounding and white or gray- 
ish in color. The gills on the under surface extend on to the 
stalk-like attachment to the wood. For more complete details 
concerning the life history and control of the wood-rotting 

fungi, see page 64. 

Reference 

Learn, C. D. Studies on Pleurotus ostreatus Jacqu. and Pleurotus 
ulmarius Bui. Annales Mycol. 10:542-556, pis. 16-18. 1912. 

White Butt-Rot 

Caused by Fames applanaius Fries 

The heartwood of the lower part of the trunk and roots of 
maple is sometimes destroyed by this rot. The decayed 
wood is whitish, light in weight and has many white-stuffed 
tunnels running in the horizontal direction. The sporophores 
of the causal fungus are shelf-like, woody bodies, with a smooth 
brownish upper surface and a white under surface. Further 
details concerning this heartwood-rot will be found under 
poplar diseases, on page 310. 



CHAPTER XXVI 
OAK DISEASES 

Over fifty species of oak (Querciis) are native in the United 
States. Many of these are important timber-trees. No region 
is without one or more species of oak, except the northern Rocky 
INIountains and the treeless plains. Although many kinds of 
oak occur on the Pacific Coast and in the Southwest, the most 
important forest-species grow in eastern and central United 
States. Many oaks are used for shade and ornament. 

The oak is more destructively affected by wood- and root- 
rots than any other important deciduous timber-tree. These 
diseases are also common in oaks used for ornament. JVIany 
species of fungi cause leaf-spots and powdery mildews. White 
oak, especially in the East, is more or less seriously affected by 
leaf-blight caused by the same fungus which occurs on syca- 
more (see page 333) . This disease often results in defoliation. 
In the South the leaf-blister is very common and often de- 
structive. The twig-blight and Strumella canker described 
below cause the death of many oaks in the East. 

Leaf-Blight 

Caused by Gnovionia veneta (Sacc. and Speg.) Klebahn 

Several kinds of oaks, especially the white oak, are attacked 
commonly by this leaf-blight. Sycamores (or plane-trees) are 
more seriously affected by the same disease. The spots de- 
veloped on the leaves may vary from small isolated light 
brown areas to large coalescing spots which involve a large 
portion of the leaf (Fig. 44). When the spots occur on the 

237 



238 



MANUAL OF TREE DISEASES 



veins, large areas are killed and the tip of the leaf frequently 
dies. The dead areas become light brown and very much 
wrinkled. Minute darker brown pustules the size of a pin- 
head or smaller are scattered over the dead area. Small 
globules of sticky spores are developed from these pustules 
in rainy weather and the spores may be washed to all parts 




Fig. 44. — Leaf-blight of oak. 

of the tree, causing the infection of other leaves. The twigs 
are sometimes affected, but this symptom is less frequent in 
oak than in sycamore. The life history of the causal fungus 
is imperfectly known and is discussed under sycamore dis- 
eases, page 333. Control measures are also the same as for 
this disease on sycamore. 



OAK DISEASES 



239 



Leaf-Blister 

Caused by Taphrina ccerulescens (Mont, and Desm.) Tulasne 

Practically all species of oak seem to be affected by leaf- 
blister. It is found throughout the United States and Europe. 
Although occurring commonly in this range it does no par- 
ticular damage except in southern United States, where it 
is epiphytotic in 
favorable seasons 
and defoliation 
results. It is re- 
ported that the 
growth of the tree 
is seriously im- 
paired and the 
individual is 
sometimes killed 
by repeated de- 
foliation. 

Symptoms. 

The blisters 
make their ap- 
pearance on the 
leaves before they 
are full grown. 
The spots are at 
first grayish or 
bluish on the un- 
der surface and 
yellowish above. 
A bulging of the leaf is soon apparent, the convex side of the 
spot usually being on the upper side of the leaf (Fig. 45). The 
blisters vary from a quarter to a half inch or more in diameter 




Fig. 45. — - Leaf-blister of oak. 



240 MANUAL OF TREE DISEASES 

and often become confluent, causing the leaf to curl. So far 
as is known, there is only the one period of infection and no 
subsequent spread to the other leaves of the tree occurs. 
Practically all the leaves of the tree may be infected, however, 
and where the blisters are numerous the leaves fall. 

Cause. 

Leaf-blister of oak is caused by the fungus Taphrina cceru- 
lescens. This fungus belongs to the family Exoascacese, all the 
members of which are parasitic and cause leaf-curls, leaf-blisters, 
plum-pockets, witches'-brooms and other types of over-growths. 
The common orchard disease, peach leaf-curl, is caused by a 
closely related form and is similar to oak leaf-blister in many 
ways. There are no fruiting-bodies formed by these fungi. 
The spores are borne in asci which stand free on the surface of 
the blistered or curled area. From the production of the spores 
which takes place as the blisters are forming, until infection 
occurs the next season, nothing is known concerning the life 
history of this entire group of fungi. No other stage of de- 
velopment is suspected but it is thought that the spores simply 
rest until the next spring and are present in some way so that 
they can infect the unfolding leaves. In the case of peach 
leaf-curl, cold wet weather following a warm period, at the time 
the buds are bursting, causes epiphytotics. Similar weather 
conditions may result in more extensive infection in the case 
of oak leaf-blister, but no observations are recorded on this 
point. 

The mycelium does not enter the tissue of the oak leaf. It 
simply penetrates the cuticle of the lower epidermis and lies 
in contact with the outer walls of the epidermal cells. The 
enzymes of the fungus diffuse into the leaf and cause a marked 
reaction on the part of the leaf-tissues. The lower epidermal 
and spongy mesophyl cells increase in number and the palisade 
and upper epidermal cells increase greatly in size, causing the 



OAK DISEASES 241 

leaf at the infected point to become much thicker. The ex- 
pansion of the affected area laterally, due to the increased 
number and size of the cells, causes it to bulge and thus the 
blister is formed. All the cells of the mycelium then increase 
greatly in size and push the cuticle off. Within each mycelial 
cell which is now an ascus, the spores are formed. 

Control. 

Apparently no spraying experiments of value have ever been 
made for the control of leaf-blister of oaks. The method used 
to control peach leaf-curl should be tried. It is, therefore, 
suggested that the trees be sprayed with bordeaux mixture 
4-4-50 or lime-sulfur 1-8 at any time after the leaves fall 
and before the buds swell. The spraying should be thorough, 
since the solution must coat every twig and bud to accomplish 
the desired results. Peach leaf-curl is easily controlled by a 
single application of any good fungicide in this way. The 
spores must, therefore, in some way be present on the outside 
of the twig or bud scales and the spray mixture kills them. 
(See Hesler, L. R., and Whetzel, H. H. Manual of fruit dis- 
eases, pp. 277-283. 1917.) 

Reference 

Wilcox, E. M. A leaf-curl disease of oaks. Alabama Agr. Exp. 
Sta. Bui. 126 : 171-187, pi. 1, figs. 1-3. 1903. (Bibliography 
given.) 

Powdery Mildews 

Caused by Microsphcera alni (Wallr.) Salmon, M. alni var. extensa 
(Cooke and Peck) Salmon, Phyllactinia corylea (Pers.) Karst. 
and Erysiphe trina Harkness 

Four species of powdery mildew fungi (besides the brown 
mildew, see page 243) are known to attack the leaves of oaks 
in the United States. The first and third species mentioned 
above occur commonly throughout the country on the leaves 



242 MANUAL OF TREE DISEASES 

of many kinds of trees (Fig. 46). The second species is a variety 
of the first, seemingly confined to eastern, southern and central 
United States, while the fourth is so far reported only from 
California. All of these fungi cause powdery white patches on 




Fig. 46. — Powdery mildew on oak leaf. 

both sides of leaves, but do little damage. The black or brown- 
ish fruiting-bodies can be seen scattered or in clusters over the 
affected area of the leaf. The life history and methods of con- 
trol of powdery mildew fungi are discussed on page 37. 



OAK DISEASES 243 

Brown Mildew 

Caused by Sphcerolheca lanestris Harkness 

The leaves and twigs of several species of oak are often at- 
tacked by this powdery mildew fungus in southern, central 
western and extreme western United States. The mycelium 
grows externally on the under sides of the leaf, the spots at 
first being white and mealy but later appearing as a dark brown 
felt due to a color change in the mycelium. The entire under 
surface of the leaf may be covered as well as the growing twigs. 
When infection occurs early in the season, the brown felt may 
completely cover the young leaves and twags, causing the leaves 
to cease growth and remain dwarfed. The black fruiting- 
bodies are buried in the mycelium on the under sides of affected 
leaves. For a fuller discussion of the life history and control 
of the powdery mildews, see page 37. 

Large Leaf-Spot 

Caused by Monochcetia Desmazierii Sacc. 

The leaves of red oak are affected by the large leaf-spot in 
the southern Appalachians. The same disease affects chestnut 
leaves in that region. The spots when fully developed are 
very large, often being from one to two inches or more in di- 
ameter. Two or three such spots cause the death of most of 
the leaf-tissue. The center of the spot is pale green or yellow 
and is surrounded by concentric bands of red and brown. 
The colored bands are less distinct on the under surface of the 
leaf. Small black fruiting-bodies, arranged in clusters, dot 
the affected area. The spores from these fruiting-bodies cause 
the infection of other leaves. Fuller details concerning this 
disease are given under chestnut diseases, page 139. Many 
other leaf-spots occur on oak. A general discussion of the 
leaf-spots will be found on page 27. 



244 



MANUAL OF TREE DISEASES 



Twig-Blight 

Caused by SphcBropsis malorum Berkeley ( = Physalospora cydonice 

Arnaud) 

This twig-blight is common on chestnut oak in central 
eastern United States. White oak and chestnut are also oc- 
casionally affected by the same disease. The 
t' smaller branches and twigs of trees of all ages 

may be killed. 

Symptoms. 

The leaves wither and turn brown. The 
mycelium of the causal pathogene grows in the 
bark and sapwood. The diseased bark becomes 
sunken and wrinkled (Fig. 47). Small black 
fruiting-bodies break through the outer bark. 
Under the dead bark, the sapwood is dark 
colored. The mycelium extends for several 
inches in the sapwood above and below the 
bark-lesion. This is evident to the unaided eye 
as a black streak when the bark is peeled from 
the twig. 

Cause. 

The fungus causing this twig-blight is known 
as Sphceropsis malorum. It occurs as a weak 
Twig-canker on parasite or saprophyte on the bark and twigs of 
oak caused by many kinds of woody plants. The New York 
lorum!'^^^^ ^" apple canker, black-rot and frog-eye leaf-spot of 
apple are caused by this fungus. Spores ooze 
from the black fruiting-bodies produced on the dead bark and 
may be washed by the rain to other parts of the tree. The 
fungus also rarely produces a perithecial stage which is known 
as Physalospora cydonice. 



OAK DISEASES 245 

Control. 

The diseased twigs and branches should be pruned from the 
tree. This may be done most efficiently in midsummer, as the 
dead leaves show more plainly. Early the next spring after 
the new leaves appear, all leafless twigs and branches should be 
removed. If these measures are not taken, large trees may 
often be killed after a few years. Care should be exercised to 
prune the twigs at least six inches below the cankered area, 
since the mycelium which spreads in the sapwood must all be 
removed (see under symptoms). 

Reference 

Ingram, Delia E. A twig blight of Quereus prinus and related species. 
Jour. Agr. Res. 1 : 339-346, pi. 38, figs. 1-7. 1914. 

Strumella Canker 

Caused by Strumella coryneoidea Saec. and Winter 

This canker of oak has been found to be common and de- 
structive in Pennsylvania. Although not definitely reported 
elsewhere, the fungus is known to occur in Missouri, Massa- 
chusetts and New York. Its range may thus be supposed to 
include northeastern United States. In Pennsylvania the 
canker is found on white, scarlet, red, yellow and chestnut oak. 
It also occurs destructively on the American chestnut. The 
most damage is reported on red and yellow oak. 

Symptoms. 

Two types of cankers with intermediate gradations are de- 
scribed. The most conspicuous form is found on red and 
yellow oak and resembles the European apple-tree canker, 
caused by Nedria gaUigena. The development of the cankers 
of this type is slow. They are elliptical in outline and consist 
of a depressed decayed center surrounded by concentric folds 



246 MANUAL OF TREE DISEASES 

of callus. The tissue around the canker is irregularly swollen, 
causing badly deformed trunks. 

The cankers gradually girdle the trunk and the trees are 
either blown over or die. Suckers are formed in abundance 
just below the cankers. On young smooth-barked trunks, 
another type of canker is formed which is at first a light yellow- 
ish raised area of bark and later develops into a sunken dead 
surface which quickly girdles the stem. When the bark is 
peeled from these cankers, thin sheets of white or pale brownish 
mycelium are exposed. 

On the surface of the affected bark of both types of cankers 
are numerous small black nodules which are the fruiting-bodies 
of the causal fungus. 

Cause. 

This canker of oaks and chestnut is caused by the fungus 
StrumeUa coryneoidea. No ascus stage has been found con- 
nected with this species and it is known only by the conidial 
fruiting-bodies. Inoculations have not been made with this 
fungus to determine fully its pathogenicity. The fungus is found 
invariably associated with the cankers and has been isolated 
and grown in pure culture. The black nodules on the cankers 
which have not girdled the trunk do not produce spores and 
are abortive. As soon as the trunk is girdled, however, nu- 
merous brownish powdery pustules burst through the bark. 
The spores of the fungus are borne free on the surface of these 
pustules and are believed to be carried by the wind. The 
mycelium penetrates the wood deeply and causes a weakening 
of the trunk. Infection usually occurs through a small branch 
stub and from this center the mycelium spreads in all directions. 

Control. 

No definite control measures are suggested for this canker. 
The ordinary surgical methods of canker treatment, however, 



OAK DISEASES 247 

will apply (see page 351). Care must be taken to remove the 
affected wood beneath the cankered area or the mycelium may 
spread into the healthy bark. 

References 

Heald, F. D., and Studhalter, R. A. The Strumella disease of oak 

and chestnut trees. Pennsylvania Dept. Forestry Bui. 10 : 1-15, 

pis. 1-12. 1914. 
Buekhdut, W. A. The undesirability of red and black oak because of 

fungus disease. Pennsylvania Agr. Exp. Sta. Ann. Rept. 1899 : 

250-252. 1900. 

Brown Checked Wood-Rot 

Caused by Polyporus sulphureus Fries 

This important wood-rot is commonly found throughout the 
United States in oak, chestnut, maple, walnut, butternut, lo- 
cust and alder. It has also been reported in white spruce in 
Maine. In Europe this disease is important in certain conifer 
as well as deciduous trees. Although not as destructive in the 
forests of the Northeast as some other diseases, it is the most 
common wood-rot of shade and ornamental oaks. The sap- 
wood and bark are affected and the tops of trees and large 
limbs are killed when thus girdled. The causal fungus lives 
saprophytically in all kinds of timber. 

Symptoms. 

The characters of the decay caused by the sulfur fungus 
serve readily to identify it, even in the absence of the yellow 
sporophores. The heartwood is usually first to be decayed. 
Gradually, however, the sapwood and bark are invaded and 
the living cells of these tissues are killed. The more com- 
pletely decayed wood is often bordered by a wide slightly dis- 
colored zone. The decayed wood becomes reddish brown and 
has the appearance of charcoal except in color. It is easily re- 
duced to powder by a blow. In the process of shrinkage which 



248 



MANUAL OF TREE DISEASES 



accompanies the decay, the affected wood splits into cubes by 
radial and circumferential cracks. The mycelium then grows 
into and fills the cracks and forms tightly woven sheets (Fig. 48). 




Fig. 48. — Brown cliecked vvuod-rot iii oak. 

The sporophores of the sulfur fungus are easily recognized. 
They emerge in late summer from old branch wounds or di- 
rectly from the bark where the mycelium has decayed the 
sapwood. At first they appear as one large or several small 
sulfur-yellow, soft and watery knobs of mycelium. These 



OAK DISEASES 



249 



quickly grow larger and form a number of Individual or closely 
over-lapping shelves, from one to several inches wide (Fig. 49). 
The upper surface of the shelves is bright orange-yellow marked 
with redder areas, while the under 
surfaces are sulfur-yellow and ap- 
pear honeycombed . The substance 
of this mature fruiting-body is 
tough but very watery. Insects 
rapidly invade it and through 
their work and decay caused by 
bacteria and possibly other fungi, 
the fruiting-body is quickly de- 
stroyed. What remains of it soon 
dries and becomes white and brit- 
tle. The mycelium in the wood 
lives from year to year and pro- 
duces these yellow sporophores 
annually. The young sporophores, 
collected before the shelves are 
fully matured, are among the best 
of the edible fungi. 

Cause. 

Brown checked wood-rot is 
caused by the fungus known as 
Polyporus sulphureus. The spores 
from the tubes on the under sur- 
face of the sporophores are wind- 
blown and infect the exposed 
heartwood at branch wounds. 
Certain deposits left by the mycelium of the fungus cause 
the reddish brown discoloration. For further details con- 
cerning the life history and control of the wood-rot fungi, 
see page 64. 




Fig. 49. — I'l uiiiug-budies of I'oly- 
porus sulphureus on. an oak. 



250 MANUAL OF TREE DISEASES 

References on Brown Checked Wood-Rot 

Schrenk, Hermann von, and Spaulding, P. Red heart-rot caused by 

Polyporus sulphureus. In Diseases of deciduous forest trees. 

U. S. Dept. Agr. Bur. PI. Ind. Bui. 149 : 37-39. 1909. 
Schxenk, Hermann von. Polyporus sulphureus (Bull.) Fr. In Some 

diseases of New England conifers. U. S. Dept. Agr. Div. Veg. 

Phys. and Path. Bui. 25 : 40-44. 1900. 
Atkinson, G. F. Polyporus sulphureus. In Studies of some shade 

tree and timber destroying fungi. Cornell Univ. Agr. Exp. Sta. 

Bui. 193 : 208-214, figs. 64-70. 1901. 
Hartig, R. Polyporus sulphureus Pr. In Die Zersetzungserschei- 

nungen des Holzes etc., pp. 109-113, pi. 14. 1878. 

Common White Wood-Rot 

Caused by Fames igniarius Fries 

Oaks, especially those species belonging to the black oak 
group, often are found with the heartwood reduced to a white 
punk. Beech and poplars, especially the aspen and balm of 
Gilead, are the most destructively and commonly affected of 
the various kinds of deciduous trees attacked by this fungus. 
In Europe this is the most important of the wood-rots of the 
oak in the forest. In the United States, the brown checked 
wood-rot of oak seems to be more destructive. This is es- 
pecially true outside the forest, where shade and ornamental 
oaks are concerned. The sapwood of oak is more commonly 
invaded than is the sapwood of the other trees affected, re- 
sulting in stag-head and dead limbs. The sporophores and 
nature of the rot which are similar for all kinds of trees are 
described under poplar diseases, on page 305. 

White Pocket Heartwood-Rot 

Caused by Polyporus Rheades Fries ( = Polyporus dryophilus Berkeley) 

The heartwood of many species of oaks and sometimes of 
poplars^ is destroyed by this disease. Although found in oaks 
practically over the entire United States, this rot is particu- 



OAK DISEASES 251 

larly destructive and common in the Southwest and along the 
Pacific Coast. In poplar it is found rarely and then often fol- 
lowing the common white wood-rot caused by F. igniarius. The 
white pocketed rot of the heartwood of oaks is confined largely 
to the upper portions of the larger and older trees. 

Symptoms. 

The first evidence of this rot in oaks is a discolored water- 
soaked area in the heartwood. Later delignification results in 
the medullary-rays turning white. In longitudinal section 
this produces a mottled appearance of white irregular lines 
running lengthwise and broader white areas joining these at 
intervals. The wood between these white areas is slightly dis- 
colored. In more advanced stages, the white areas involve 
adjacent tissues and become more extensive and less definitely 
linear. The small amount of discolored wood between the 
white areas remains firm. Irregularly distributed in the de- 
cayed wood are brown areas varying from an eighth to a half 
inch across. The wood surrounding the white pocketed surface 
is discolored and water-soaked. In some species the symptoms 
vary slightly from those described above. In chestnut oak 
the spring-wood of the annual rings is yellowish white and the 
tissue between these concentric zones is light brown. In 
poplar the rot as seen in cross-section produces alternate zones 
of whitish and yellow tissue. The same brown areas are present 
as in the oak. 

The sporophores formed at branch wounds on the oaks are 
flat and shelf-like or hoof-shaped, but when formed directly 
from the bark they are almost globose. A peculiar diagnostic 
character of these sporophores consists in a hard, granular 
sandstone-like core with radiating white mycelial strands run- 
ning through it. This core extends back into the rotted wood 
of the tree for a short distance. The upper surface is rusty 
yellow or brown and at first is hairy but later becomes smooth. 



252 MANUAL OF TREE DISEASES 

The under surface is brown as is the inside structure, including 
the granular core. 

Cause. 

The white pocketed rot of oaks and poplars is caused by the 
fungus Polyporus Rheades which is also known by the name 
P. dryoyhilus. The sporophores described above are annual. 
The rot may be confined largely to the branches and upper 
part of the trunk or the tree may be rotted from the base to top. 
Infection occurs most commonly in broken branches, from 
which the mycelium extends down into the trunk. When in- 
fection takes place through dead side branches or at the base 
of the tree, through fire scars, the rot may extend the entire 
length of the trunk. For fuller details concerning the life 
history of wood-rot fungi and the nature of the decay caused 
by them, see page 64. 

References 

Hedgcock, G. G., and Long, W. H. Heart-rot of oaks and poplars 
caused by Polyporus dryophilus. Jour. Agr. Res. 3 : 65-80, pis. 
8-10. 1914. 

Sehrenk, Hermann von, and Spaulding, P. Piped-rot of oak and 
chestnut. In Diseases of deciduous forest trees. U. S. Dept. 
Agr. Bur. PI. Ind. Bui. 149 : 39-40, pi. 5. 1909. (Note : The 
piped-rot of oak described is due to P. Rheades and that of chest- 
nut to P. croceus.) 

Hartig, R. Polyporus dryadeus Fr. In Die Zersetzungserschei- 
nungen des Holzes etc., pp. 125-128, pi. 17. 1878. (This is a 
discussion of the rot due to P. Rheades and not P. dryadeus.) 

String and Ray Butt-Rot 

Caused by Polyporus Berkeleyi Fries 

This heartwood-rot of the base of oak trees is found through- 
out eastern and central United States. It is not known to be 
as common or destructive as several of the other wood-rots of 
oaks. Mature and over-mature trees are affected. It is never 
found in the tops of trees but is limited to the base of the trunk 



OAK DISEASES 



253 



and the larger roots. The decay extends from the surface of 
the ground upward in the heartwood for a distance of one to a 
few feet and in its final stages leaves a large hollow cavity. 

Symptojns. 

When badly rotted trees are cut, they fall after the thin shell 
of heartwood is cut through and the trunk carries with it the 
partially rotted hollow cylinder of wood from the stump. The 
odor of the freshly cut rotted wood is very strong and resembles 
anise oil. The first indication of the decay is seen in longi- 
tudinal section as a yellowish or whitish area from four to eight 




Fig. 50. — Fruiting-body of Polyporus Berkeleyi. 

inches long. The summer-wood in this region is delignified 
and the individual fibers are separated by the dissolving of the 
cementing layer between them. As the decay progresses the 
dense whitish summer-wood is completely destroyed. This 
leaves the medullary-rays and strands of porous spring-wood 
intact. The interwoven rays and strings of wood are brownish 
at first but soon are covered with whitish mycelium. The 
strands slowly become more brittle and finally collapse, leaving 
a hollow cavity. The decayed area becomes larger and is 
bordered by a zone of whitish wood with the string and ray 
rot stage projecting into the hollow cavity. 

The sporophores arise from the exposed larger roots or may 



254 MANUAL OF TREE DISEASES 

appear to come from the soil near the base of the tree. In all 
cases, however, they will be found attached by mycelial strands 
to the roots. The sporophores are usually large and may occur 
as two to five overlapping shelves or as a single more or less 
circular, expanded, toadstool-like body supported on a thick 
stalk (Fig. 50). The center of the upper surface is depressed 
where it is attached to the stalk. The upper surface is white 
or yellowish, while the under surface is whitish and covered 
with large angular honeycomb-like pores. 

Cause. 

The string and ray butt-rot of oaks is caused by Polyporus 

Berkeleyi. The spores are borne around the inner surfaces of 

the angular pores of the sporophores. Infection takes place in 

wounds at the base of the tree, such as fire-scars. The life 

history and control of wood-rotting fungi are discussed more 

fully on page 64. 

Reference 

Long, W. H. Three undescribed heart-rots of hardwood trees, espe- 
cially of oak. Jour. Agr. Res. 1 : 109-128, pis. 7-8. 1913. 

Wet Heartwood-Rot 

Caused by Hydnum erinaceus Fries 

Oak and other deciduous trees are affected by this wet heart- 
wood-rot. White and red oaks are most commonly affected. 
The disease is common in central United States and is some- 
times found in other parts of the country. 

Symptoms. 

In the early stages of this decay, the wood becomes lighter 
in color and the woody tissue between the medullary-rays is 
destroyed. Later the entire structure of the wood disappears 
and there remains only a white soggy mass. Large cavities 



OAK DISEASES 255 

or entirely hollow trees are thus formed. The cavities are 
filled or lined with yellowish mycelium. 

The fruiting-bodies of the causal fungus are formed annually 
at wounds or insect tunnels. They are globose and may be as 
large as a foot across. The upper surface is hairy and covered 
with drops of water. The under surface and the margin of the 
fleshy fruiting-body are covered with numerous long pendent 
spines or teeth. Insects soon destroy the fruiting-body. 

Cause. 

The wet heartwood-rot of oaks and other trees is caused by 
Ilychium erinaceus. The spores are borne over the outer sur- 
face of the teeth on the under side of the fruiting-body. They 
are disseminated by the wind and infection takes place in 
wounds of all sorts. P^urther details concerning the life history 
and control of wood-rots will be found on page 64. 

Reference 

Schrenk, Hermann von, and Spaulding, P. Disease caused by Hydnum 
erinaceus. In Diseases of deciduous forest trees. U. S. Dept. 
Agr. Bur. PI. Ind. Bui. 149 : 44-4.5, pi. 7. 1909. 

Honeycomb Heartwood-Rot 

Caused by Stereum subpileatum Berkeley and Curtis 

This heartwood-rot of oak is common in Arkansas, Missis- 
sippi and Louisiana. It is also found in Kentucky, Ohio, 
Missouri, Virginia and Florida and probably is generally dis- 
tributed over southern United States. Several species of oaks 
are affected. The sapwood is not destroyed and the sporophores 
of the fungus occur only on dead fallen trees or on dead areas 
in living trees. 

Symptoms. 

The affected wood is at first slightly discolored and water- 
soaked. Light colored areas appear at various places in the 



256 MANUAL OF TREE DISEASES 

discolored region and develop into white pockets. They are 
located partially in the porous spring-wood of one ring and in 
the summer-wood of the adjoining ring. Later the pockets 
become hollow and have a white lining. They become larger 
in time until finally limited by reaching a large medullary- 
ray on each side. Only a narrow layer of brownish wood 
separates the adjoining pockets. In longitudinal sections, the 
pockets are seen to be from three to five times as long as w^de. 
The discolored area extends from one to six feet beyond the 
region showing the pockets. In the first stages of the decay, 
this rot closely resembles the white piped butt-rot caused by 
Poly pontes croceu.s (see page 258). The latter rot usually ex- 
tends its activities more rapidly upward than radially, causing 
the decay of a few annual rings, while the honeycomb-rot in 
white oak, at least, spreads uniformly in both directions. 
Freshly cut wood affected by this rot is said to have the odor 
of old honeycomb. 

The sporophores are rarely available to identify this rot in 
living trees, except when a large area of the affected heartwood 
is exposed. Sporophores develop on the felled timber in a 
year or two and continue to form for several years. They are 
from a quarter of an inch to two inches wide, rather thick 
shelving bodies occurring one over the other in long rows. The 
upper surface is at first downy and light yellowish brown, later 
becoming smooth and gray. Concentric furrows mark the 
upper surface into zones which vary in color. The under 
surface is light yellowish brown and smooth. 

Cause. 

The honeycomb heartwood-rot of oaks is caused by the 
fungus, Stereum subpileatum. The fruiting-bodies described 
above are annual structures which become dry and persist 
through the winter and may revive the following season. The 
spores are borne over the entire smooth under surface of the 



OAK DISEASES 257 

shelves. The fungus finds entrance into the tree where heart- 
wood is exposed at fire-scars, branch wounds and the like. 
While usually found in the base of the trees, it sometimes oc- 
curs in the tops. The sapwood of the living tree is not affected, 
but when the tree is felled the mycelium grows into the sapwood 
and causes a similar decay. 

Control. 

In the forest this rot can be controlled by preventing fires, 
which are responsible for the scars that furnish a ready en- 
trance point for infection. Likewise it is essential to remove or 
burn dead and diseased oaks that are standing, as well as cull 
logs, for on these the sporophores will continue to form for 
several years. These measures will also keep several of the 
other butt-rots and heartwood-rots of oaks under control. 

Reference 

Long, W. H. A honeycomb heart-rot of oaks caused by Stereum sub- 
pileatum. Jour. Agr. Res. 5:421-428, pi. 41. 1915. 

Soft Heartwood-Rot 

Caused by Polyposis obtusus Berkeley 

Black oaks in eastern and central United States are affected 
by this heartwood-rot. Several trees are usually found affected 
in a group where the disease occurs. 

Symptoms. 

The affected heartwood is lighter in color than the normal 
wood and finally becomes almost white. The wood does not 
check and retains its normal fibrous character. It, however, 
is weak and breaks easily. The rot progresses rapidly and the 
trunks are weakened so that they snap off during wind-storms. 

The fruiting-bodies appear annually on the side of the trunk. 
They are more or less hoof-shaped and at first white and spongy, 
s 



258 MANUAL OF TREE DISEASES 

Later they become yellowish or brown. The upper surface 
and the rounded edge and outer margin of the lower surface 
are hairy. The remainder of the under surface is covered 
with roundish or sinuous pores, the edges of which are irregular, 
making the under surface rough. 

Catise. 

The soft heartwood-rot of black oaks is caused by Polyporus 
ohtiisu^. The spores borne within the tubes on the under sides 
of the fruiting-bodies are blown about by the wind. Infection 
usually takes place by the spores entering the tunnels made 
in the wood by the insect, Prionoxystus robinice. From the 
tunnels the mycelium spreads upward and downward in the 
wood. The fruiting-bodies are usually produced at the insect 
burrow where infection occurred. For further details con- 
cerning the life history and control of wood-rot fungi, see 
page 64. 

References 

Spaulding, P. A disease of black oaks caused by Polyporus obtusus 

Berk. Missouri Bot. Garden Rept. 16:109-116, pis. 13-19. 

1905. 
Schrenk, Hermann von, and Spaulding, P. Soft rot of oaks caused 

by Polyporus obtusus. In Diseases of deciduous forest trees. 

U. S. Dept. Agr. Bur. PI. Ind. Bui. 149 : 41-42, fig. 5. 1909. 

White Piped Butt-Rot 

Caused by Polyporus croceus Fries ( = P. Pilota; Schw.) 

This wood-rot is found in oak and chestnut. The wood of 
the roots and base of the trunk is most commonly affected, 
although when dead branches are common it may be found in 
the upper part of the trunk. It has proved destructive in 
Arkansas, Virginia and New York and probably is generally 
distributed throughout eastern and central United States. 
The decayed wood is at first filled with white areas which en- 



OAK DISEASES 259 

large and become hollow cavities with white margins. These 
pockets become so abundant that the summer-wood is largely 
converted into strings of white fibers leaving the wood brittle 
and easily broken. Further details concerning this white 
pocket- or piped-rot will be found under chestnut diseases, 
page 150. 

Straw-Colored Butt-Rot 

Caused by Polyporus frondosus Fries 

This rot of the heartwood of the base of oak and probably 
of chestnut is found in eastern and central United States but 
does not seem to occur very commonly or destructively. It 
develops only in the base of the trunk. The wood is not en- 
tirely destroyed and the trees do not become hollow. 

Symptovis. 

In longitudinal section the upper advancing margin of the 
decay is indicated by long, slender, white lines extending for 
several inches upward into the sound wood. In advance of 
the white lines, the wood is water-soaked and reddish in color. 
The rotted wood is at first white and later tan- or straw-colored. 
Most of the tissue is delignified but is firmly held together by 
the less affected medullary-rays. The cut ends of the trunks of 
felled trees become reddish brown after a month or two. 

The sporophores of the causal fungus arise from exposed or 
buried roots near the base of the tree. They are composed of 
a fleshy stem which is much branched, the ends of the 
branches forming small flat over-lapping shelf-like structures. 
The whole fruiting-body is more or less globose. The upper 
surfaces of the shelves are gray or drab and the under surfaces 
white. 

Cause. 

The straw-colored butt-rot of oak is caused by Polyporus 
frondosus. The spores from inside the tubes on the under sides 



260 MANUAL OF TREE DISEASES 

of the shelves of the fruiting-body cause infection in wounds at 
the base of the tree. The life history and control of the wood- 
rot fungi will be found discussed on page 64. 

Refekence 

Long, W. H. Three undeseribed heart-rots of hardwood trees, espe- 
cially of oak. Jour. Agr. Res. 1 : 109-128, pis. 7-8. 1913. 

White Wood-Rot 

Caused by Fomes Everhartii (Ellis and Gall.) Schrenk 

This wood-rot has been found common in black jack oak and 
probably occurs in other species. It has not been fully de- 
scribed. It is said to resemble closely the common white wood- 
rot caused by Fomes igniarius. The rot extends into the sap- 
wood. The sporophores of the causal fungus also resemble 
those of Fomes igniarius. They are shelf-like and rarely hoof- 
shaped. The upper surface is at first brown, but later becomes 
black and checked by many fissures. The under surface and 
margin are brown. The pores in the under surface are very 
small. 

Reference 

Schrenk, Hermann von, and Spaulding, P. Heart-rot of oaks caused 
by Fomes Everhartii. Ln Diseases of deciduous forest trees. 
U. S. Dept. Agr. Bur. PL Ind. Bui. 149 : 48, pi. 3. 1909. 

White Butt-Rot 

Caused by Fomes applanalus Fries 

The heartwood of the lower part of the trunk and roots of 
oak is sometimes destroyed by this rot. The wood becomes 
whitish and light in weight but retains its fibrous structure. 
The rotted wood when split shows numerous sinuous white- 
stuffed tunnels resembling the work of insects. The sporo- 
phores oi the causal fungus are often found at wounds near the 



OAK DISEASES 261 

base of the trunk. The form on oak is usually thick, with a 
dark gray, rough upper surface, an acute margin and a slightly 
roughened, white under surface. This heartwood-rot is more 
fully described under poplar diseases, on page 310. 

White Root-Rot 

Caused by Polyporus dryadeus Fries 

Many species of oaks are affected by a white root-rot which 
occurs apparently throughout the range of the oaks in the 
United States and Europe. Although not as important as 
many of the other wood- and root-rotting fungi, oaks growing 
under adverse conditions are often found affected. The ulti- 
mate result of the attack is the death of the tree or it may be 
uprooted during wind-storms. 

Symptoms. 

The first indication of the rot is a reddish or brownish colora- 
tion of the inner bark-tissues. The adjacent sapwood then be- 
comes reddish brown and watery. The discoloration advances 
into the wood and the color of the decayed areas changes to 
white. The bark becomes loosened and shreds into strips. 
The rot finally involves the larger roots and extends into the 
butt of the tree but does not progress above the surface of the 
ground. The smaller roots are completely decayed and look 
like pith. They are light in weight and when twisted break 
into concentric layers. Older partially decayed roots, in 
longitudinal section, show the white or cream-colored rotted 
bark and wood bounded by a dark brownish zone one to three 
inches wide which marks the progressing area of change from 
normal wood to white punk. The radial and longitudinal 
whitish bands appearing in the affected wood are due to the 
mycelium of the fungus which is aggregated in the porous 
regions of the annual rhigs. White patches of mycelium ap- 



262 MANUAL OF TREE DISEASES 

pear on the surface of the outer bark of affected roots. The 
largest roots may be rotted to the center and the decayed wood 
is finally spongy and easily crushed. 

The sporophores of the causal fungus form on exposed roots 
when the tree is blown over or at the very base of the trunk, 
arising at the surface of the ground. They are large, irregu- 
larly shaped masses of a corky or woody texture (Fig. 51). 
When developing, they are watery, and large drops of water 




Fig. 51. — Friii ting-body of Polyporus dryadeus. 

often form on the outer growing margin. These drops leave 
depressions in the surface. The upper surface is uneven 
and light brown, changing with age to darker brown and 
black. The under part is oblique to the surface of the 
ground in the thicker forms and more or less horizontal in 
the thinner forms. The pores in the under surface are 
soon stuffed with mycelium, making them invisible. The 
outer margin of the sporophore is thick and rounded. In- 
sects soon destroy the under surface and outer margin but the 



OAK DISEASES 263 

black partially rotted central mass may remain for years at- 
tached to the root or trunk. 

Cause. 

The white root-rot of oaks is caused by the fungus Polyporus 
dryadeus. The sporophores are rarely found but the rot is not 
uncommon. The method of infection has not been described. 
No fungous strands are found in the soil around the rotted 
roots, as in the shoe-string root-rot, and the trees apparently 
are not attacked in groups. The spores produced in the tubes 
of the sporophore probably find lodgment on exposed roots 
and thus initiate infection. 

The mycelium grows first in the bark and then into the sap- 
wood and heartwood. The brownish watery zone of the first 
stage of decay is due to the production of a brownish liquid 
which fills the cells. Later this disappears and the cell con- 
tents and a portion of the cell-walls are dissolved. There is 
little delignification, although the wood appears white. The 
ease with which the wood splits into concentric rings and frac- 
tures crosswise is due to the very thin walls left in the porous 
part of the annual ring and medullary-rays. The tree suffers 
general decline because of the destruction of the conducting 
tissue of the roots and they may be killed outright when the 
larger roots are attacked first. 

Reference 

Long, W. H. Polyporus dryadeus, a root parasite on the oak. Jour. 
Agr. Res. 1 : 239-250, pis. 21-22. 1913. 



CHAPTER XXVII 
PINE DISEASES 

Over thirty species of pine (Pinus) occur as forest-trees in the 
United States. No region of the country where trees grow is 
without representatives of this important group. A large part 
of the timber of the country is made from pines. The various 
native pines and many exotic species and varieties are used 
for ornamentals. 

Pine is subject to many destructive diseases wherever it 
grows. The most important of these are root-rots, wood-rots, 
blister-rusts, mistletoe injury, leaf-cast and various types of 
winter-injury. The importance of these types of diseases 
varies with the species and region of the country in question. 
Pecky wood-rot and the different blister-rusts of the branches 
and trunks probably cause the most damage. The white pine 
of the northeastern states was reasonably free from important 
diseases until the introduction from Europe of the blister-rust 
fungus. Pines outside of the forest often suffer severely from 
winter-drying and other types of injury due to extremes in 
temperature. 

Seedling Root-Rot 

Caused by Rhizina undulata Fries 

The seedlings of several species of pines in the forests of 
northwestern United States are killed by this root-rot. The 
fungus is also present in several eastern states and may cause 
similar damage. The roots cf seedlings three to six years old 
are killed. Examination shows the. roots and a quantity of 

264 



PINE DISEASES 265 

soil to be matted together by white myceHum. Brown fruiting- 
bodies are formed on the surface of the soil around diseased 
trees. This fungus is more fully discussed under hemlock 
diseases, page 177. 

Leaf Blister-Rusts 

Caused by fungi of the genus Coleosporium 

Several species of the genus Coleosporium grow in the needles 
of pines, occasionally causing defoliation. These rust-fungi 
require, in addition to the pine, some other kind of plant on 
which to continue their life history. Such an alternation of 
hosts is not uncommon in the rust-fungi. In the case of the 
Coleosporium leaf-rusts of pine, seciospores are produced in 
the yellow blisters pushed out from the pine needles. These 
spores cannot reinfect the pine, but they may cause infection 
of the leaves of certain near-by flowering plants. Here the 
development of the fungus is continued and urediniospores 
are formed. The urediniospores infect other plants of the 
same kind and by a succession of several generations of these 
spores the rust may become prevalent during the summer for 
a considerable distance away from the pine which developed 
the seciospores. In the autumn a brown layer of another type 
of spores (teliospores) is formed on the plants which produced 
the urediniospores. The teliospores germinate while they are 
still attached to the host and minute basidiospores are formed. 
These spores are short-lived and are blown about by the wind. 
If they come into contact with the needles of the proper species 
of pine, they may initiate a new infection. Thus the seasonal 
life history of the fungus is completed. 

By eliminating the flowering plant, which must be present 
for the fungus to complete its development, the rust is incapable 
of existing. The minimum distance for the successful inter- 
change of spores between the pine and the alternate host is 
variable. Control is sometimes accomplished when all the 



266 MANUAL OF TREE DISEASES 

flowering plant hosts are removed, so that none exists within 
a thousand feet of the pines. A safer distance would be a 
quarter or a half mile, depending on the contour of the land 
and the nature of the surrounding vegetation. The elimina- 
tion of all the plants of the kind required by the blister-rust 
fungi is not easily accomplished. Nevertheless, it is an efficient 
and sure method of control, if the eradication is thoroughly 
done. For a further discussion of the factors involved in carry- 
ing out eradication methods, see under blister-rust of five- 
needle pines, page 274. 

Many of the species of Coleosporium that are known in the 
uredinial and telial stages on various weed plants have not 
been connected with the blister-rust stage on pine needles. 
Either this has not been found and described, or the relation 
between the stages on the pine and weed host has not been 
definitely proved to represent the life history of a single species. 
When all the stages are known, the fungus is called by its 
Coleosporium name. When only the blister-rust stage is 
known on the pines, it is classified in the large form genus 
Peridermium and is given a temporary specific name. 

Below are given brief descriptions of the blister-rusts of the 
needles of pines, with their distribution, the species of pine 
afl^ected and the alternate weed hosts, so far as these facts are 
known. In most cases these blister-rusts cannot be identified 
except by microscopic examination. 

An inconspicuous blister-rust is known to occur in IMaryland 
on scrub pine. The name of the causal fungus is Coleosporium 
inconspicuum (Long) Hedgcock and Long. The alternate weed- 
hosts on which its life history is completed are the tickseeds 
(Coreopsis xerticiUata and C. major). 

Scotch pine needles are affected by CoJeosporium sonchi- 
arvensis (Persoon) Lev. This disease has been reported only 
from Wisconsin. The fungus was imported from Europe. 
The yellow blisters are small, being about one-sixteenth of an 



PINE DISEASES 267 

inch long or smaller and only project slightly above the surface 
of the needle. The life history is completed on the sow thistles 
(species of Sonchus). 

A blister-rust of the needles of lodge-pole and western yellow 
pine is caused by Peridermumi montanum Arthur and Kern. 
It is known from central Montana westward and northward. 
The yellow pustules on the pine needles are about one-sixteenth 
of an inch long and project only slightly above the surface of 
the needle. The alternate weed hosts are probably the differ- 
ent species of Arnica. 

A blister-rust of the needles of short-leaf pine is caused by 
Peridermium interinedium Arthur and Kern and is known from 
central Missouri and Arkansas to central North Carolina. 
The yellow pustules on the needles are from one-sixteenth to 
one-eighth of an inch long and project above the surface of the 
needle about one-sixteenth of an inch. The alternate weed 
host has not been determined. 

A conspicuous leaf blister-rust is known on loblolly, long-leaf, 
sand, short-leaf, spruce, western yellow, pitch, pond and Cuban 
pines. The causal fungus is Coleosyormm vernoniae B. and C. 
( = C. elephantopodis (Schw.) Thiim.) and is found from Vir- 
ginia to Florida and westward to central Texas. The yellow 
pustules on the needles are larger than those of the other pine 
leaf blister-rusts. They are about one-fourth of an inch long 
and three thirty-seconds of an inch high. The alternate weed 
hosts of this rust are different species of ironweed and elephant's- 
foot (Vernonia and Elephantopus). 

A leaf blister-rust of pitch and Norway pine is caused by 
Coleos'pormm solidaginis (Schw.) Thiim. and is known from 
IVIassachusetts and central New York southward to central 
North Carolina. Although the disease has been found only 
within the above indicated area, there is the possibility of its 
appearance on pitch and Norway pine at almost any point in 
North America, since the stages of the causal fungus on the alter- 



268 MANUAL OF TREE DISEASES 

nate weed hosts are found throughout the country. This rust is 
similar to several other blister-rusts which affect the pitch pine. 
The yellow pustules project above the surface of the needles 
from one thirty-second to cne-sixteenth of an inch. The 
alternate weed hosts are species of goldenrod and wild aster. 
The rust is able to maintain itself on these weeds without the 
presence of the pitch pine, by the wintering-over of the ure- 
diniospores which reinfect the goldenrod and aster. 

A prominent leaf blister-rust of pitch pine is caused by Cole- 
sporium campanvlcB (Persoon) Lev. and is known from New 
Jersey and central Indiana southward to central North Caro- 
lina. It differs from the other blister-rusts of pitch pine in that 
the yellow pustules on the needles are much larger and tongue- 
shaped. They are from one-sixteenth to one-eighth of an inch 
long and project above the surface about one-sixteenth of an 
inch. The alternate weed host is the tall bellflower (Cam- 
pamila americana) . 

Another blister-rust of pitch and Norway pine is caused by 
Coleosporiumdelicatuhim (Arthur and Kern) Hedgcockand Long. 
It is found along the Atlantic coast from Massachusetts to 
Florida. It may have a much wider range than this, since its 
alternate stages on the weed host, species of Euthamia, have 
been found from Maine to Kansas and southward to West 
Virginia and Texas. The leaves of the pines show in the spring 
very small yellow blisters, from one thirty-second to one-fourth 
inch long and scarcely protruding above the epidermis of the 
needle. 

Short-leaf, long-leaf, pitch and loblolly pine are affected by a 
needle blister-rust in central eastern and southeastern United 
States, caused by Coleosporium ipomccw (Schw.) Burrill. The 
pustules on the pine needles are flattened, narrow and about 
one-sixteenth of an inch long. The life history is completed 
on many species of mcrning-glory (Ipomoea). 

Short-leaf and loblolly pines in Georgia and North Carolina 



PINE DISEASES 269 

have been affected by a needle blister-rust caused by Coleo- 
sporium ierebinthinacecB (Schw.) Arthur. The pustules are 
tongue-shaped and project about one-sixteenth of an inch from 
the needles. The life history of this fungus is completed on 
rosin- weed (species of Silphium). 

The needles of scrub and probably of short-leaf pine from 
Pennsylvania to Illinois and southward are attacked by Coleo- 
sporium helianthi (Schw.) Arthur. The blisters are tongue- 
shaped and project from the leaf about one-sixteenth of an inch. 
The life history of the fungus is completed on sun-flower (Heli- 
anthus). 

The needles of long-leaf, loblolly and pitch pine are attacked 
hy Peridermium fragile Hedgcock and Hunt. The blisters are 
narrow and inconspicuous. The alternate host for the com- 
pletion of the life history of this fungus is not known. 

In Florida the needles of loblolly and spruce pine are attacked 
by Peridermium mimihivi Hedgcock and Hunt. The blisters 
are low and a little narrower than long. The alternate host for 
the completion of the life history of this rust is unknown. 

The needles of piiion are attacked by Coleosporium rihicola 
(C. and E.) Arthur, practically throughout the range of this 
species in Colorado, New INIexico and Wyoming. The blisters 
appear on the pine needles while snow is still present. The 
alternate hosts of this fungus are species of currant and goose- 
berry (Ribes). The pustules on the currant and gooseberry 
leaves are larger and more prominent than the felt-rust (see 
page 274). 

References 

Arthur, J. C, and Kern, F. D. North American species of Perider- 
mium. Bui. Torrey Bot. Club, 33 : 403-438. 1906. 

Arthur, J. C, and Kern, F. D. North American species of Perider- 
mium on pine. Mycologia 6 : 109-138. 1914. 

Hedgcock, G. G., and Hunt, N. Rex. New species of Peridermium. 
Mycologia 9:239-242. 1917. 

Hedgcock, G. G. Notes on some western Uredinese which attack 
forest trees. Mycologia 4 : 141-147. 1912. 



270 MANUAL OF TREE DISEASES 

Leaf-Rust 

Caused by Gallowaya pini (Galloway) Arthur 

The leaves of scrub pine are commonly affected by this rust 
throughout its range in central eastern United States. This 
disease differs from the blister-rusts of pine needles in the 
teliospores being borne on the pine and no alternate host being 
required (see page 265). Yellow spots occur near the tips of 
the leaves. On these spots are formed linear, reddish orange 
pustules which burst through the epidermis. These pustules 
may be a half inch long. The bright color soon fades and they 
are inconspicuous. The teliospores germinate in the spring, 
producing basidiospores which infect other scrub pine needles. 

Leaf-Cast of White Pine 

Caused by Hypoderma slrobicola Tubeuf 

White pine is sometimes injured in eastern Ignited States 
by this leaf-cast. Pitch pine and hemlock are reported to be 
affected by the same disease. The affected needles at first 
show yellowish spots and later turn reddish yellow and brown. 
The tissues of the twig may also be killed. Later in the season 
several small elliptical black fruiting-bodies appear on the 
outer surface of the needles. The fruiting-bodies are mature 
the following spring. They split open and the spores are shot 
into the air during prolonged rain periods. For further details 
concerning the leaf-cast diseases, see page 38. 

References 

Graves, A. H. Leaf blight. Lophodermium braehysporum Rostrup. 

1 71 Notes on diseases of trees in the southern Appalachians 1. 

Phytopathology 3 : 133-139, figs. 5-10. 1913. 
Spaulding, P. The present status of the white-pine blights. U. S. 

Dept. Agr. Bur. PI. Ind. Circ. 35 : 1-12. 1909. 



PINE DISEASES 271 

Brown Felt-Blight 

Caused by Neopeckia Coulleri (Peek) Sacc. 

The brown felt-blight of pine is a common disease at altitudes 
from six to eleven thousand feet above sea level in northwestern 
United States. The leaves and twigs are covered and matted 
together by an abundant growth of brown mycelium. It is 
indistinguishable from the brown felt-blight of other species of 
conifers. The behavior of this disease is in every way parallel 
to the similar disease of spruce which is discussed on page 317. 

Leaf-Cast and Witches'-Broom of Western Yellow Pine 

Caused by Hypoderma deformans Weir 

This disease is destructive to western yellow pine in the 
Northwest and on the Pacific Coast. A similar disease on 
Jeffrey pine in California may be caused by the same fungus. 
The needles of western yellow pine of all ages are killed. Seed- 
lings and young trees may be destroyed outright. On older 
trees the needles of the season become infected, gradually turn 
yellow and brown and fall from the twigs. They may remain 
on the tree for one cr mere years, however, and this gives the 
appearance that the needles of all ages are affected. The 
mycelium enters the young twigs. The affected twigs remain 
stunted and large brooms are formed. The brooms hang 
from the limb. The black fruiting-bodies of the fungus 
break through the epidermis of the leaves in the autumn. 
They are mature the following spring and may shed their sp:;res 
throughout the summer. Further details concerning the leaf- 
cast diseases will be found on page 38. 

Reference 

Weir, J. R. Hypoderma deformans, an undeseribed needle fungus of 
the western yellow pine. Jour. Agr. Res. 6 : 277-288, pi. 32, 
figs. 1-4. 1916. 



272 MANUAL OF TREE DISEASES 

Twig-Blight 

Caused by Cenangium ferruginosum Fries 

This disease is reported as common and destructive in Europe 
on Scotch, Austrian and white pines and on European silver 
fir. In this country very Httle mention of it has been made. 
It is reported on white pine in Ohio and the causal fungus has 
been found on long-leaf, western yellow and Monterey pine. 
On these latter trees the fungus was not shown to be parasitic. 
Mature trees are more often affected than younger ones and 
the disease is unknown on trees less than five years old. In 
Europe this disease is said to occur in epiphytotics which sweep 
over large forest areas. 

SymptoTTis. 

The terminal buds of affected twigs die in the spring. Later 
the older needles turn red and die from the base to the tip. 
The dead needles fall and leave the twigs bare. 

Small fruiting-bodies are formed on the dead twigs and 
branches. In wet weather the fruiting-bodies open and are cup- 
shaped, measuring about one-eighth of an inch across. During 
dry weather they close and are more or less globose. In this 
condition they are dusty brown or black but when they are open 
the inner surface of the cup is yellowish or dirty greenish yellow. 

Cause. 

This twig-blight of pine is supposed to be caused by the 
fungus Cenangium jerruginosum. Asci containing ascospores 
are borne on the yellowish inner surface of the fruiting-bodies. 
The ascospores are forcibly ejected and borne by the wind for 
long distances. Other types of fruiting-bodies, resembling 
those described above, are also formed which produce simple 
spores. These, however, are not known to play any important 
part in the life history of the fungus. There is some question 
whether this fungus is primarily responsible for this disease. 



PINE DISEASES 273 

It seems more probable that winter-drying and other tj'pes of 
winter-injury may account for the injury and that the fungus 
is secondary and only semi-parasitic. 

Control. 

The only measure of control known is to prune off the dead 
twigs and burn these, together wdth all other brush and refuse 
from coniferous trees that may be in the vicinity. 

References 

Fink, Bruce. Injury to Pinus strobus caused by Cenangium abietis. 

Phytopathology 1 : 180-183, pi. 26. 1911. 
Schwarz, Frank. Die Erkrankung der Kiefern durch Cenangium 

Abietis, pp. 1-126, pis. 1-2. 1895. 

Mistletoe Burls and Witches'-Brooms 

Caused by Razoumojskya campijlopoda (Englem.) Piper, and R. amcri- 
cana (Nutt.) Kuntze 

Western yellow and lodge-pole pine are affected respectively 
by these two dwarf mistletoe parasites. In northwestern 
United States much damage results from the diseased condition 
they cause. The general result of burl and witches '-broom 
formation is a reduction in foliage which causes slow^ growth 
and finally death when infection is heavy. Likewise, the dis- 
eased areas of bark offer ready places of entrance for insects 
and wood-rotting fungi. Trees of all ages are affected. Trees 
with the lower branches or trunk affected early in life suffer 
more severely than those infected later. The brooming of the 
lower branches diverts a large part of the growth energy of the 
tree and the tops are dwarfed and die, causing stag-headed or 
spike-topped trees. 

Symptoms. 

The roots from the germinating mistletoe seeds enter the 
leafy twigs or through wounds in the bark of older branches. 



274 MANUAL OF TREE DISEASES 

Swellings of the limb are first formed and later many abnormal 
branches are sent out and ragged broom-like growths are pro- 
duced. Burls at the base of the branches and on the side of 
the trunk also develop where the roots of the parasite find a 
foothold. The mistletoe plant may die but the stimulus still 
continues to cause the abnormal growth. The brooms may 
become so heavy when burdened with ice and snow that the 
limb breaks. The needles of the old brooms are usually smaller 
and shorter-lived than on healthy branches. For a general 
discussion of the mistletoe diseases of trees, see page 54. 

Reference 

Weir, J. R. Mistletoe injury to conifers in the northwest. U. S. 
Dept. Agr. Bui. 360 : 1-38, pis. 1-4, figs. 1-27. 1916. 

Blister-Rust of Five-Needle Pines 

Caused by Cronartium ribicola Fischer de Waldheim 

The fungus causing the blister-rust of five-needle pines is 
native in Europe. With the extensive use of the American 
white pine in western Europe for forest-planting, it became 
widely distributed on this tree and was soon recognized as an 
important enemy of the white pine. As early as 1890 and 1900, 
it was prevalent in all the countries of western and northern 
Europe and was known in Siberia and Japan. The fungus 
is supposed to have been originally confined to the Swiss stone 
pine of Europe, which is not very seriously affected by it. In 
Germany, France, England and other countries of western 
Europe the blister-rust soon became so prevalent and de- 
structive that the further use of the American white pine in 
reforestation was largely abandoned. Previous to this time 
large numbers of white pine were grown in the forest nurseries, 
and this disease was found to affect seriously a large percentage 
of the trees in some regions. 



PINE DISEASES 275 

Even with these facts known, no definite action was taken 
in the United States to prevent the introduction of this fungus, 
and in 1906 it was first found at Geneva, New York. Later,' 
in 1909, it was discovered in recently imported seedling stock 
in New York, Vermont, New Hampshire, jMassachusetts, 
Connecticut, Pennsylvania, Indiana and Ohio. The demand 
for white pine nursery stock both for forest and ornamental 
plantings had far exceeded the amount produced in this country 
at that time, and several hundred thousand trees had been im- 
ported annually from Germany and France. It is, therefore, 
not surprising that numerous diseased pines were found in the 
different states where this stock was planted. Although at- 
tempts were made to eradicate the known diseased trees, the 
fungus is now generally prevalent in the New England states 
and New York and is known in restricted areas in Wisconsin 
and Minnesota. 

All pines which have their needles in fascicles of five are ex- 
pected to be susceptible. It is definitely known that the 
eastern white pine, western white pine and sugar pine are 
susceptible. As yet the fungus has not been found in western 
United States where the two important western species of 
this group grow. The damage that may result to the five- 
needle pines in the forest in this country cannot be prophesied 
at this time. Young trees and the younger branches of older 
trees are most seriously affected. In plantations of European 
stock in New York state not more than one per cent of the 
trees were ever found affected. However, in several places 
under actual forest conditions in northeastern United States 
where the fungus has existed unnoticed for many years, a much 
larger percentage of the stand is affected. 

The fungus causing white pine blister-rust requires the pres- 
ence of some species of gooseberry or currant for the comple- 
tion of its life history. The spores developed on the pines 
cannot infect other pines but must lodge on the leaves of cm'- 



276 



MANUAL OF TREE DISEASES 



rant or gooseberry bushes in order to continue the cycle of de- 
velopment. Spores are then produced throughout the summer 
on these plants which cause the infection of other goose- 
berries and currants. In the autumn 
another type of spores (teliospores) is 
developed on the affected currants and 
gooseberries and from these are formed 
basidiospores which cause the infection 
of the young branches of five-needled 
pines. The distribution of this fungus 
on the pines, therefore, is dependent on 
the presence or absence of gooseberries 
and currants, and if present the amount 
of damage done is somewhat dependent 
on their abundance. Unfortunately sev- 
eral species of these plants occur as 
common weeds practically throughout 
the range of the five-needle pines in the 
United States. 

SymptoTTis. 

The young leaf-bearing twigs are in- 
fected and the mycelium grows in the 
bark and may extend into the larger 
branches and trunks. The affected bark 
is usually swollen, but the tissue remains 
normal and healthy in appearance for 
two or three years. In the second or 
third spring after infection occurs, the 
prominent fruiting-pustules of the fungus 
appear on the bark (Figs. 52 and 53). 
These blister-like pustules are irregularly 
„ ^„ ^,. , , hemispherical or elongate, one-eighth to 

Fig. 52. — Blister-rust on ^ i i j 

twig of white pine. one-half mch across and orange-colored. 




PINE DISEASES 



277 



The covering of the blisters breaks and a fine yellow powder 
of thousands of spores dusts out and is blown away by the 
wind. The blister stage on the pine is formed in early spring 
and by midsummer the white 
coverings of the blisters disap- 
pear and only rounded depres- 
sions remain in the bark to mark 
their location. The area of bark 
from which the blisters are pro- 
duced usually dies but the my- 
celium extends into the surround- 
ing healthy bark. The yellow 
blisters are produced year after 
year from the newly invaded 
bark until on older trees cankers 
several feet long are sometimes 
formed. Usually the branch or 
trunk is soon girdled and the 
parts of the tree beyond the 
girdled point die. The fungus 
cannot exist except in living 
tissue and, therefore, is not har- 
bored after the affected part of 
the tree is killed. Young trees 
with the trunk affected show a 
stunted and compact growth and 
a slight yellowish color instead 
of the normal green. 

Infected currant and goose- 
berry leaves show slightly yellow- 
ish spots which are more distinct 
on the under surface. Small 
yellowish blisters are pushed out t^ -o t^, , ^ 

» , , , , . biG. 06. — Blister-rust on trunk of 

irom tne lower epidermis and young white pine. 




278 



MANUAL OF TREE DISEASES 



when the covering is broken, a rounded mass of yellow 
spores (urediniospores) is exposed (Fig. 54). Later in the 




Fig. 54. — Cronariium ribicola (urediiiiai stage) on under side of currant loaf. 

season, from the same lesions several slender brown bristle- 
like structm-es are pushed out from the under sides of the 

leaves (Fig. 55) . When 
the affected areas of 
the leaf are numerous, 
these brown bristles so 
completel}^ cover the 
under side of the leaf 
that it appears as 
coarse brown felt, and 
thus the common name 
for this disease on cur- 
rants and gooseberries 
is felt-rust. But little 
damage is caused to 
the affected bushes, al- 
though defoliation may 
occur earlier than nor- 
mally when the leaves 
are heavily infested. 
r, ,■ i- ; ^* 1- 1 + N The species of currant 

Lronarlium rimcola (teiial stage) on ^ 

Felt-rust. and gooseberry vary 




Fig. 55 

under side of currant leaf 



PINE DISEASES 279 

greatly in susceptibility. Tlie cultivated black currant is 
most susceptible, the under sides of the leaves being often 
completely covered with the felt-stage. Gooseberries in general 
are more resistant than currants. 

Cause. 

The blister-rust of five-needle pines and the felt-rust of cur- 
rants and gooseberries are caused by the fungus, Cronartium 
ribicola. Before the stages on the two kinds of plants were 
known to be caused by the same fungus, the stage on the pine 
was called Peridermium strobi. The life history of this fungus 
has been indicated above. The seciospores formed in the 
blisters on the pine branches infect the leaves of gooseberry 
and currant. After a period of development in the leaf-tissue, 
urediniospores are formed which infect other gooseberry and 
currant leaves. From the same pustules the teliospores are 
developed in long hair-like masses. These spores are not 
disseminated but germinate and produce small, globose spores 
(basidiospores) on the short germ-tubes. The basidiospores 
are shot from their attachment and may cause infection of the 
pine. In this way, although the pine is not infected by the 
seciospores produced in the blisters, the mycelium of the 
fungus after about two months' growth in the currant or 
gooseberry produces the kind of spore which will infect the 
pines. 

Weather conditions in relation to the spread and severity 
of attack of this fungus are not fully understood. Moisture 
is necessary for the germination of the different spores and 
from analogy to other similar diseases, it would be expected 
that the stage on currants and gooseberries would be more 
abundant in wet seasons. The distance over which the spores 
are transported by the wind depends largely on prevailing 
air currents and the topography of the region. In a dense 
growth of underbrush in the forest the fungus would not be 



280 MANUAL OF TREE DISEASES 

expected to spread as rapidly in a given season as it would in 
more open country. 

Control. 

Although repeated attempts had been made since 1896 to 
secure a federal law which w^ould prevent the entry of foreign 
stock likely to harbor and introduce dangerous fungi and in- 
sects, such a law was not enacted until 1912. The blister-rust 
fungus had by that time become established in various locali- 
ties in northeastern United States. The extermination of the 
fungus was attempted where it was known. In New York 
all the known areas where foreign white pine stock was planted 
were inspected yearly. The diseased trees and all currant 
and gooseberry bushes within five hundred feet of them were 
destroyed. When the fungus was found prevalent in western 
Massachusetts in the fall of 1915, more extensive surveys were 
planned for 1916 and as the result, the fungus was found to be 
generally prevalent throughout the territory east of the Hudson 
River and Lake Champlain. In 1917 it was found practically 
throughout New York state. Despite the previous attempts 
at its eradication in isolated areas and any efforts that may 
be made at general control in the future, the fungus is now so 
well established in this country that it will continue to spread 
and exist wherever conditions are favorable. 

In certain regions in which the white and other five-needle 
pines are important as ornamentals, the native wild species of 
gooseberry and currant are very scarce. Such conditions 
exist in the lower Hudson River valley and on Long Island. 
In these regions this disease could easily be controlled if the 
cultivated garden varieties of gooseberry and currant were 
eliminated. However, when one neighbor grows one of these 
plants and the next has five-needle pines to protect, no generally 
satisfactory agreement will be reached in most cases. The 
elimination of currants and gooseberries for a distance of one- 



PINE DISEASES 281 

half mile from the pines will probably control this rust. If 
this distance is not possible, a separation of five hundred feet 
or more will be partially beneficial. 

In forested areas where wild currants and gooseberries are 
common, the further growing of white pine may have to be 
abandoned. The elimination of the bushes over extensive 
areas will probably never prove as profitable as planting or 
encouraging natural reproduction of some other species of 
tree suited to the conditions. Where currants and gooseberries 
are not very abundant and the experiment of eliminating them 
is thought practicable, results may be obtained if the work is 
vigorously prosecuted year after year. The total cost and 
the possibilities of failure must influence the planning of this 
kind of control when timber values alone are to be considered. 

References 

Spaulding, P. The blister rust of white pine. U. S. Dept. Agr. 

Bur. PI. Ind. Bui. 206: 1-88, pis. 1-2, figs. 1-5. 1911. (Bibli- 
ography given.) 
Spaulding, P. The white-pine blister rust. U. S. Dept. Agr. Farmers' 

Bui. 742 : 1-15, pi. 1, figs. 1-5. 1916. 
Spaulding, P. New facts concerning the white-pine blister rust. 

U. S. Dept. Agr. Bui. 116: 1-8. 1914. 
Spaulding, P. Foresters have a vital interest in the white-pine 

blister rust. Proc. Soc. Am. For. 11 : 40-47. 1916. 
Atwood, G. G. Emergency bulletin on the blister rust of pines and 

the Eiu*opean currant rust. New York Dept. Agr. Hort. Bui. 

2 : 1-15, pis. 1-2. 1909. 
Paul, B. H. The pine blister. New York Conservation Com. Bui. 

15: 1-18, figs. 1-8, map. 1. 1916. 

Sweet-fern Rust 

Caused by Cronartium comptonicB Arthur 

This rust disease occurs on two- and three-needle pines in 
eastern United States and is commonly known as blister-rust. 
It is found on the native pitch, scrub, loblolly, western yellow. 



282 MANUAL OF TREE DISEASES 

jack, lodge-pole, Jeffrey, Norway and short-leaf pines and on 
the imported Scotch, Austrian and mugho pines. Only very 
young trees are generally affected and it is most important as a 
nursery and young plantation disease. It is known to have 
caused the death of a large number of the susceptible pines 
in certain nurseries in Massachusetts, Connecticut, New York 
and Michigan. The common weeds, sweet-fern (Comptonia 
asplenifolia) or sweet-gale {Myrica Gale) must be in the vicinity 
of the pines for this fungus to complete its life history. If 
this plant is not present, the unaffected trees will not be en- 
dangered by the diseased pines. 

Symptoms. 

This rust produces symptoms on two- and three-needle 
pines very similar to the blister-rust which occurs on five- 
needle pines (see page 276). Small branches and the trunks of 
young trees are affected. Slight enlargements are usually 
iformed. On these swollen areas yellowish blisters are pushed 
out in early spring. The arched covering breaks and the 
orange-colored spore-mass inside dusts out as a fine powder 
and is blown away. 

On the sweet-fern and sweet-gale {Comptonia asplenifolia 
and Myrica Gale), small yellowish pustules are formed on 
the under sides of the leaves in summer, followed later by 
brown bristles which project from the same spots. These 
structures are similar to those formed on gooseberry and 
currant leaves affected with felt-rust (see page 277). 

Cause. 

The sweet-fern rust of two- and three-needle pines is caused 
by the fungus Qronariium comptonicB { = Peridermium comp- 
tonicB Orton and Adams), a close relative of the blister-rust fungus 
on white pine. The life history and control of this rust-fungus 
is similar to the white pine blister-rust except that it has 



PINE DISEASES 283 

its alternate stages on sweet-fern and sweet-gale instead of on 
currants and gooseberries (see page 279). 

References 

Spaulding, P. Notes on Cronartium Comptoniae, II. Phytopathol- 
ogy 3 : 308-310. 1913. 

Clinton, G. P. Cronartium Comptonise Arth. (I. Peridermium pyri- 
forme Pk.). Connecticut Agr. Exp.. Sta. Ann. Rept. 1907- 
1908:380-383, pi. 28. 1908. 

Weir, J. R. Observations on the pathology of the jack pine. U. S. 
Dept. Agr. Bui. 212: 1-10, pi. 1, figs. 1-4. 1915. 

Spaulding, P. Notes on Cronartium Comptonise III. Phytopathology 
7:49-51. 1917. 

CoMANDRA Rust 

Caused by Cronartium comatulrce Peek 

This is one of the six blister-rust diseases of the stems of 
pines in the United States. Although known commonly as 
blister-rust, it is here called the Comandra rust of pines to 
distinguish it from the other five similar diseases. The Co- 
mandra rust occurs on pines having two or two to three needles 
in a bundle and not on the three-needle pitch pines. It has 
been found on lodge-pole, jack, western yellow and table-moun- 
tain pine, in several eastern, north-central and western states. 
A part of the life history of the causal fungus is spent on species 
of Comandra and on these plants it has been found over the 
entire northern and central part of the United States from the 
Atlantic to the Pacific. In the western states the Comandra 
rust is an important disease of the pines which are susceptible. 
In certain regions a large percentage of the younger trees 
has been found affected or killed. Older trees are rarely 
attacked. In Pennsylvania the disease causes the death of 
many young table-mountain pines. 

Symptoms. 

The trunks and limbs of trees less than two or three inches 
in diameter are attacked. Spindle-shaped swellings are pro- 



284 MANUAL OF TREE DISEASES 

duced which may be several inches long except in very young 
trees where no swellings are noticeable. The trunk may 
become infected by the fungus extending into it from infected 
branches. The fruiting-bodies appear on the affected bark 
in early spring. They are yellowish blisters, usually about 
a quarter of an inch or smaller in diameter and may be longer 
than broad. The covering of the blister breaks and the spores 
are blown away as a fine orange-colored powder. 

The spores from the yellow blisters infect the leaves and 
younger stems of species of Comandra. Small yellowish or 
reddish pustules are formed on light colored areas of the leaf 
and a little later brown bristles project from the same spots. 
The plants are dwarfed and often premature defoliation occurs 
when the leaves are badly affected. 

Cause. 

The Comandra rust of pines is caused by the fungus Cronar- 
tium comandrce {=Peridermium pyriforme Peck). The secio- 
spores formed in the blisters on the pine bark cause the infection 
of the leaves and young stems of Comandra. On that host 
urediniospores are formed which infect other Comandra plants. 
The urediniospores are closely followed by the production of 
the bristle-like teliospore columns, the individual cells of which 
germinate and produce the basidiospores. These latter spores 
are wind-borne and may cause the infection of the pines, if 
they are near by. Both the pines and species of Comandra 
must be present in the same locality for this fungus to exist 
on the pines. 

Control. 

The elimination of the species of Comandra from the vicinity 
of nurseries and young plantations is necessary if this disease 
is to be controlled. In the forest the diseased trees may be 
destroyed as a measure of protection for the young growth 



PINE DISEASES 285 

coming on. However, a few will always escape detection and 
if the Comandra plants are abundant, several pines may be- 
come infected during a season when only one existed in the 
spring. 

References 

Arthur, J. C, and Kern, F. D. The rediscovery of Peridermium pyri- 
forme Peek. Science 38 : 311-312. 1913. 

Hedgeock, G. G., and Long, W. H. A disease of pines caused by Cro- 
nartium pyriforme. U. S. Dept. Agr. Bui. 247 : 1-20, pis. 1-2, 
fig. 1. 1915. 

Hedgeock, G. G., and Long, W. H. Two new hosts for Peridermium 
pyriforme. Jour. Agr. Res. 5 : 289-290, pi. 27. 1915. 

Orton, C R., and Adams, J. F. Notes on Peridermium from Pennsyl- 
vania. Phytopathology 4 : 23-26, pi. 3. 1914. 

Castilleja Rust 

Caused by Cronartiuni coleosporioides (D. and H.) Arthur 

This blister-rust disease occurs from the Rocky Mountains 
to the Pacific Coast Range and from Canada to Mexico. It 
is exceedingly destructive to lodge-pole and western yellow 
pine. Large knots and cankers are formed on lodge-pole pine 
which at times are similar to the oak rust of pines (see page 287). 
The trunks of many trees five inches in diameter are girdled 
by the cankers, which may be from two to eight feet long. The 
bark soon dies and the death of the tree or branch follows. 
Fifty per cent of the stand is sometimes seriously affected. 
This fungus requires the presence of the weeds, Castilleja 
miniata and other species of the same genus, in the vicinity 
of the pine in order to complete its development. When these 
plants do not exist, this fungus cannot affect the pines. 

Symptoms. 

Both young and old trees are affected. Small trees in the 
nursery show but little enlargement of the affected branches 
or trunk. Large orange-colored blisters burst through the 



286 



MANUAL OF TREE DISEASES 



bark, and the spores within are shed as a fine powder. The 
affected Hmbs of older trees may show but Httle swelHng or, as 
in the case of lodge-pole pine, large knots or galls and cankers 

are produced (Fig. 56). After the first 
crop of blisters is formed, the bark 
usually dies and the mycelium extends 
its activities to the healthy bark around 
the dead area. This process of en- 
largement of the canker or gall con- 
tinues until the limb or trunk is 
girdled and death results. 

On the under sides of the leaves of 
species of Castilleja, small yellowish 
spots appear during the summer. 
Later numerous brownish bristles are 
pushed out from these spots. The 
appearance of the leaf is very similar 
to currant and gooseberry leaves af- 
fected with felt-rust (see page 277). 

Cmise. 

The blister-rust which affects west- 
ern pines and species of Castilleja is 
caused by the rust-fungus Cronartium 
coleosporioides {= Peridermium filamen- 
tosum, the Rocky Mountain form of 
Peridermium Harknessii). The life 
history of this rust is similar to that 
of Cronartium ribicola described on 
page 279. The seciospores germinate 
and infect the Castilleja leaves. Ure- 
diniospores propagate the fungus on this host throughout the 
summer and the teliospores and basidiospores are formed in 
late summer. Infection of the pine takes place in the autumn. 




Fig. 56. — Blister-rust or 
Castilleja rust on lodge-pole 
pine. 



PINE DISEASES 287 

Control. 

In the western forests, the grazing animals keep the Castilleja 
plants down to a minimum. Where grazing is not common, 
these plants grow in large numbers and predispose the pines 
to infection. All Castilleja plants should be eradicated for a 
distance of a half mile around nurseries in which the species 
susceptible to this rust-fungus are grown. 

References 

Weir, J. R., and Hubert, E. E. A serious disease in forest nurseries 
caused by Peridermium filamentosum. Jour. Agr. Res. 6 : 781- 
785. 1916. 

Hedgcoek, G. G. Notes on some western Uredineae which attack 
forest trees. II. Phytopathology 3 : 15-17. 1913. 

Oak Rust 

Caused by Cronartium cerebrum (Peck) Hedgcoek and Long 

The blister-rust of pines, which is here called the oak rust, 
is generally distributed throughout the United States. It has 
been found on a large number of species of two- and three- 
needle pines ; lodge-pole, jack, western yellow, short-leaf, Mon- 
terey, Sabine, long-leaf, pitch, Jeffrey, loblolly, scrub, gray, knob- 
cone. Coulter, Piiion, Norway, sand, spruce and pond. Con- 
siderable damage is caused to certain of these species in different 
sections of the country. Along the Atlantic Coast and in the 
southern Appalachian Mountains, scrub pine is severely dam- 
aged. In INIichigan and IMinnesota the jack pine is affected to 
the extent that on dry lands fifty per cent of the trees are dam- 
aged. In swamps practically every tree contains one or more 
galls and witches'-brooms. In the west, the Sabine, twisted, 
Monterey and knob-cone pines are the most susceptible species. 

Syin'ptoms. 

Three types of injury are produced on the affected pines 
of all ages. When the young leafy branches are infected, 



288 MANUAL OF TREE DISEASES 

witches'-brooms are formed. The smaller branches and twigs 
are infected through injuries in the bark and abrupt globose 
or gradual spindle-shaped swellings are produced. The globose 
type of gall is found more commonly on scrub, jack, short-leaf, 
lodge-pole, sand, Pifion, Norway and spruce pine, while the 
more gradual swellings are found on Coulter, western yellow, 
Monterey, gray, loblolly and pond pine. When the swelling 
originates at the base of a branch, the adjacent tissue of the 
trunk is affected and large burls are formed. The part of the 
tree above these enlargements of the trunk and branches is 
ultimately killed. A single tree may have from one to hundreds 
of galls and several witches'-brooms. Young seedlings are 
often affected and killed. 

The fungus fruits abundantly in the spring by forming 
prominent yellowish blisters over the surface of the globose or 
spindle-shaped swellings. These are united into continuous 
convoluted ridges which resemble the appearance of brain- 
tissue. The covering of the blisters is broken and a large 
quantity of orange-colored powder dusts out and is blown away 
by the wind. 

The leaves of many species of oaks are affected by the same 
fungus. During the summer, small yellowish or reddish 
pustules are formed on the under sides of the leaves. Later 
from the same pustules numerous brown bristles are pushed 
out. The leaves of the oak are not appreciably injured by the 
fungus. 

Cause. 

This blister-rust disease is caused by the fungus Cronartium 
cerebrum { = Peridermium cerebrum, P. fusiforme and the Pacific 
Coast form of P. Harknessii). The fungi causing the blister- 
rusts of pines are closely related species having similar life 
histories. The life history of the white pine blister-rust fungus 
(page 279) serves equally well for this species with the excep- 



PINE DISEASES 289 

tion that the seciospores cause the infection of the leaves of 
species of oaks instead of the currant and gooseberry. Some 
investigations point to the possibihty that this fungus may 
be an exception to the rule in requiring the presence of 
the oak in order to have the infection of pines occur. This 
fact, together with the conditions observed in California and 
Oregon when the pines are often infected with no oaks near, 
leads to the supposition that the oak may not be neces- 
sary in the life cycle. Likewise, the fungus persists over 
winter on the evergreen oaks on the Pacific Coast. The leaves 
harbor the mycelium and new fruiting-bodies are developed 
in the spring around the dead areas produced the previous year. 
The destructive action of the fungus on pines is caused by 
the flow of resin from the diseased tissue into the conducting 
tissue of the branch and trunk. This shuts oflF the food and 
water supply and causes the death of the parts above. The 
affected bark of the enlargement dies after a few years and 
insects and wood-rot fungi enter at these places. 

Control. 

Where oaks and pines grow in close proximity, the control 
of this disease may be accomplished by eliminating the oaks, 
unless it is definitely proved that the oak is unnecessary in the 
life history. The elimination of the trees showing one or more 
galls of this disease is advisable at the time of cutting. 

References 

Weir, J. R. Observations on the pathology of the jack pine. U. S. 

Dept. Agr. Bui. 212 : 1-10, pi. 1, figs. 1-4. 1915. 
Graves, A. H. Notes on diseases of trees in the southern Appalachians 

II. Phytopathology 4:5-10, pi. 2, fig. 1. 1914. 
Meineeke, E. P. Peridermium Harknessii and Cronartium Quercuum. 

Phytopathology 6 : 225-240, figs. 1-2. 1916. 
Hedgcock, G. G., and Long, W. H. Identity of Peridermium fusiforme 

with Peridermium cerebrum. Jour. Agr. Res. 2: 247-249, pi. 11. 

1914. 



290 MANUAL OF TREE DISEASES 

PiNON Blister-Rust 

Caused by Cronartium occidentale Hedge, Bethel and Hunt 

For many years a species of Cronartium has been known 
on currants and gooseberries in Colorado, for which no bhster- 
rust stage on pines could be found. Recently the blister-rust 
caused by this fungus has been discovered on nut and single- 
leaf pine. This disease is neither common nor destructive on 
these trees, so far as observed. Slight swellings are formed. 
The blisters which push through the bark in the spring are not 
prominent. As a result of the formation of the blisters, the 
bark is broken into irregular flakes and the inner bark dies. 
The seciospores infect currants and gooseberries and produce 
symptoms on these hosts which are indistinguishable from 
those on the same plants, produced by Cronartium ribicola 
(see page 277). The fungus has been named Cronartium occi- 
dentale. It has not been found to infect five-needle pines, 
although it has been observed for years on gooseberries and 
currants in close proximity to these pines.. 

Basal Canker 

Caused by Phoma sp. ? 

In many localities in northeastern United States, more or 
less circular areas have been noted in which all the white pine 
are dead. Around these blanks some trees are often found 
which have yellowish and scanty foliage. Closer examination 
usually shows that the base of the tree at the surface of the 
ground has been girdled. The bark is dead and markedly 
constricted. Fruiting-bodies of a species of Phoma are gen- 
erally found on the bark. There is some evidence that this 
disease occurs only in the vicinity of ant-hills and it is sug- 
gested that the ants, their burrowings in the ground, or the 
aphids with which the ants associate, have some connection 



PINE DISEASES 291 

with the occurrence of the disease. So far no satisfactory 
work has been carried on to explain the real factors involved. 

References 

Graves, A. H. A preliminary note on a new bark disease of the white 

pine. Myeologia 6 : 84-87, pi. 120. 1914. 
Haasis, F. W. Dying of young pines in circles about anthills. Jour. 

Forestry 15 : 763-771, figs. 1-5. 1917. 

Pecky Wood-Rot 

Caused by Trametes pini Fries 

This is the most destructive wood-rot of conifers in the 
forests of the United States. It is commonly known as ring- 
shake, red-rot, pecky wood-rot or peckiness. The ring-shake 
character of this rot is more common in pine than in the other 
conifers affected. Infection takes place at branch wounds 
where heartwood is exposed. The mycelium penetrates 
through the wood of the branch stub into the heart of the tree. 
Here it spreads rapidly upward and downward but in the radial 
direction it spreads more slowly. The result is that a few 
annual rings of the wood are often destroyed before the wood 
within and without the affected layers is penetrated. The 
common name ring-shake is, therefore, appropriate. In the 
other conifers, however, the mycelium is usually less restricted 
and often no shake is produced. The pine wood, being rich 
in resinous materials, escapes the dq,maging action of this fungus 
in the sapwood and bark ; and pines, therefore, are rarely killed 
by it. As the mycelium advances toward the bark, quantities 
of resin are liberated. It accumulates in the sapwood and bark, 
making these tissues immune to the further penetration of the 
fungus. The white lined pockets of decay occur in the heart- 
wood. The discussion of this fungus as given under spruce 
diseases (see page 324) is in every way applicable to the pine, 
except as to the points mentioned above. The sapwood and 



292 MANUAL OF TREE DISEASES 

bark, not being affected in the pine, cause the formation of the 
fruiting-bodies to be Hmited to branch wounds where the 
branch stub forms an outlet for the mycelium. 

Red-Brown Sapwood-Rot 

Caused by Fomes pinicola Fries 

Pines, as well as spruce, fir, larch and hemlock, are every- 
where commonly affected by this red-brown sapwood-rot. 
The organism causing the rot also grows saprophytically and 
is the most common fungus on coniferous wood. The wood is 
reduced to a red-brown powdery mass which is held together 
by the many sheets of mycelium which run in all directions. 
The sporophores of the causal fungus have a red varnished 
margin and cream-colored under surface. Further details 
concerning this disease will be found under fir diseases, on page 
165. 

Brown Heartwood-Rot 

Caused by Fomes officinalis Fries (= Fomes laricis (Jaeq.) Murrill) 

In western United States pine is destructively attacked 
by this brown heartwood-rot. Larch, Douglas fir and other 
conifers are affected by the same rot. Sugar, western yellow 
and lodge-pole pine are more damaged than other species. 
The decay resembles to some extent the brown checked wood- 
rot caused by Polyponts sniphureiis. The decayed wood is 
brown or red-brown, and felts of mycelium form in checks in 
the wood. The sporophores of the causal fungus are not 
formed abundantly. They are large, globose or hoof-shaped 
bodies with a white chalky upper surface. The inner substance 
is bitter and has a mealy odor. Further details concerning 
this heartwood-rot will be found under larch diseases, on 
page 216. 



PINE DISEASES 293 

Brown Pocket Heartwood-Rot 

Caused by Fomes roseus Fries 

Pines are commonly affected by this heartwood-rot. Juniper, 
spruce, fir, larch and hemlock are also affected by the same 
disease. In the first stages, long, cylindrical pockets of brown 
charcoal-like wood are formed. Later the pockets may coalesce 
and the wood is uniformly brownish and splits into cubes. 
The fruiting-bodies of the causal fungus are either thin and 
shelf-like or hoof-shaped. The under surface is rose-colored. 
Further details concerning this heartwood-rot will be found 
under juniper diseases, on page 204. 

Red-Ray Wood-Rot 

Caused by Polyporus Ellisianus (Murr.) Long 

This wood-rot of western yellow pine has recently been 
studied in New Mexico and Arizona, where it is common in 
suppressed and over-mature trees. It is variously known as 
red-heart, red-rot, gray-rot and top-rot. This disease is thought 
to have a wide distribution, since it has been found in South 
Dakota in western yellow pine, in Vermont in white pine, and 
the fungus is known from the states of Washington and New 
Jersey. In many respects this decay-process resembles the 
yellow wood-rot of locust. 

Symptoms. 

In the early stages the central core of the heartwood is par- 
tially decayed and is reddish brown. Later, the red-brown 
wood becomes gray or whitish and is thoroughly disintegrated 
and easily pulled apart. At this stage it is also possible to 
squeeze water from the decayed mass. In cross-sections of 
affected trunks, the whitish stage is surrounded by a red-brown 
area. Radiating from this uniformly affected area are reddish 



294 MANUAL OF TREE DISEASES 

colored rays extending like spokes of a wheel toward the bark. 
In longitudinal section these rays of decay are seen to have a 
whitish core of completely decayed tissue. If the wood is 
split tangentially these rays appear as red elliptical areas with 
whitish centers. The rays become larger until they finally 
coalesce. The whitish rotted cores become so completely 
disorganized that cavities are left which are bordered by white 
rotted wood. By this manner of spreading, the fungus very 
quickly extends its activities radially, although some time 
elapses between the pushing out of the rays and the time when, 
by gradual enlargement; they coalesce. 

The fruiting-bodies of the fungus causing this rot are formed 
annually on the under sides of logs lying on the ground. They 
are white and usually resupinate incrusting layers. 

Cause. 

It is thought that the fungus causing the red-ray wood-rot 
is the same as the one called Poly poms EUisianus, although this 
has not been definitely determined. Infection results in old 
branch wounds at the top of the tree, and the mycelium spreads 
upward and downward, often producing a rotted area in the 
wood twelve to twenty feet long from a single infection. A 
more detailed discussion of the nature of wood-rots and the life 
history of the fungi causing them is given on page 64. 

Reference 

Long, W. H. A preliminary report on the occurrence of western red- 
rot in Pinus ponderosa. U. S. Dept. Agr. Bui. 490 : 1-8. 1917. 

Red-Brown Root- and Butt-Rot 

Caused by Polyporus Schweinitzii Fries 

This root- and butt-rot occurs in pine, fir, larch, spruce, 
hemlock and arbor-vitse, wherever these trees grow. The 
destruction it causes to these conifers is second in importance 



PINE DISEASES 295 

only to that caused by the pecky wood-rot. One or the other 
of these wood-rots may predominate in a given region, and 
combined they constitute a serious menace to young and old 
trees. The two rots are also often found in the same tree, the 
one in the roots and lower trunk and the other in the upper 
trunk and branches. 

Symptoms. 

The decay is first evident in the heartwood of the roots. 
The affected wood becomes yell-owish and soon splits along 
certain medullary-rays and annual rings into large cubical 
masses. The wood in this stage of decay is soft and cheesy. 
In the final stages, the wood is uniformly rotted, brittle, char- 
coal-like and red-brown in color. From the heartwood of the 
larger roots, the fungus may spread into the base of the trunk. 
At times the rot may extend upward in the trunk for several 
feet. The usual effect of this wood-rot is the uprooting of the 
weakened tree by the wind. 

The sporophores of the causal fimgus are soft, annual bodies 
and grow from exposed or superficially buried roots. They 
are red-brown, umbrella-shaped bodies with a central stalk 
and circular, undulating top. They often grow to a large 
size, being a foot or two across. The under surface of the cap 
is covered with numerous large, shallow and irregular pores. 
When old, a sugary solution is exuded from the under surface 
of the sporophores and insects quickly destroy them. 

Cause. 

The red-brown root- and butt-rot of conifers is caused by 
Polyporus Schweinitzii. The roots are infected by the my- 
celium growing in the soil from tree to tree. Also the spores 
produced in the shallow tubes of the fruiting-body may infect 
the wood which is exposed at fire wounds. For a general dis- 
cussion of the life history of wood-rotting fungi, see page 64. 



296 MANUAL OF TREE DISEASES 

The control of this root-rot would require such measures as are 
described under the shoe-string root-rot (see page 78). 

References 

Schrenk, Hermann von. Polyporus Schweinitzii. In Some diseases 

of New England conifers. U. S. Dept. Agr. Div. Veg. Phys. 

and Path. Bui. 25 : 18-24, pis. 1-2. 1900. 
Hedgeock, G. G. Notes on some diseases of trees in our national 

forests. IV. Phytopathology 4 : 181-188. 1914. 
Hartig, R. Polyporus mollis Fr. In Die Zersetzungserscheinungen 

des Holzes, etc., pp. 49-53, pi. 9. 1878. 

Yellow Root-Rot 

Caused by Sparassis radicata Weir 

Pines are seriously damaged in the Northwest by the yellow 
root-rot. In the same region fir, spruce and larch are also 
affected. Yellow sheets of mycelium are formed in the bark 
of the affected roots. Later the sap wood and in some cases 
the heartwood of the roots is decayed. Large, white, fleshy 
fruiting-bodies are produced on the ground, which are con- 
nected with the diseased roots by long tuber-like growths. 
Further details concerning this root-rot will be found under 
fir diseases, on page 170. 

Brown Root- and Butt-Rot 

Caused by Fomes annosus Fries 

Pines are occasionally affected by this root- and butt-rot. 
The wood of the roots and butt of the pine is decayed, but the 
fungus does not extend its activities into the trunk because of 
the high resin-content of the wood. The wood becomes in 
turn bluish, yellowish and red-brown. White pockets with 
black centers are visible for a time in the brown wood, but later 
these coalesce and leave the brownish summer-wood of the 



PINE DISEASES 297 

annual rings as separated sheets. The sporophores of the causal 
fungus occur on exposed or buried roots. They are perennial, 
shelving or resupinate bodies with light brown upper surface 
and a yellowish tube-layer. For further details concerning 
this disease, see under spruce diseases, on page 329. 



CHAPTER XXVIII 
POPLAR DISEASES 

A VARIETY of common names is used to designate the dozen 
or so species of Populus native in the United States. The dis- 
eases of these trees are common to the different species and the 
name poplar is used to designate the group except when certain 
species are indicated. Poplars are important forest-species. 
The common cottonwood is frequently used for shade and 
ornament in regions in which trees are not abundant, because of 
deficient rainfall. This tree is especially adapted to dry soils 
and formerly was used extensively as a street tree, until it 
was found to damage sewers and drainage pipes by clogging 
them with its roots. The European white and black or Lom- 
bardy poplar are planted frequently as ornamentals. 

Poplars are subject to several types of diseases. The leaf- 
rusts are destructive to young trees and seriously interfere 
with their growth in the plains region. The newly introduced 
European fungus which causes the poplar canker has already 
proved to be a menace to young trees in the nursery. It is 
also destructive on trees which are recently transplanted. 
The importance of this disease cannot at present be prophesied, 
since apparently it has not been in this country for any length 
of time. In the forest the common white wood-rot is the most 
destructive disease of poplars. 

Leaf-Rusts 

Caused by Melampsora Medusoe Thiim., M. ahietis-canadensis (Farl.) 
Ludwig and M. albertensis Arthur 

Three leaf-rusts of poplars are common in the United States. 
Two of these occur practically throughout the country, while 

298 



POPLAR DISEASES 299 

the other is confined to the Rocky Mountains. Injury to the 
trees resuUs from frequent defoliation. In regions of little 
rainfall where poplars are important because of their adapta- 
bility to such conditions, the rust often causes the death of 
younger trees and seriously interferes with their propagation. 

Symptoms. 

The three leaf-rusts are very similar in appearance. Yellow- 
ish, powdery pustules appear on the leaves in the summer. 
These pustules may be scattered over the leaf or they may be 
crowded over the entire surface, giving the leaves a golden 
yellow tinge that may be seen from a distance. In some 
regions the foliage may be generally infected and the entire 
trees are yellow. Later in the season, many small orange- 
yellow or purplish brown slightly raised spots appear on the leaf. 

Cause. 

The leaf-rusts of poplars are caused by three species of the 
rust-fungi, Melamysora Medusce, M. ahietis-canadensis and M. 
albertensis. The first two species affect many kinds of poplars 
throughout the United States, while the latter occurs only in the 
Rocky ]\Iountains. Urediniospores, formed in yellowish powdery 
pustules, infect other poplar leaves. The darker colored and 
slightly raised spots on the infected leaves, later in the autumn, 
contain teliospores. These spores germinate the following spring 
and produce basidiospores. The basidiospores of M. Medusoe on 
poplar were shown several years ago to infect young larch 
leaves (see page 212). Recently also it has been demon- 
strated that the basidiospores of the second fungus on the large- 
tooth aspen, at least, cause the infection of young hemlock 
needles in northeastern United States (see page 182). The 
basidiospores of the rust common on poplars in the Rocky 
Mountains cause the infection of the young needles of Douglas 
fir (see page 159). The proximity to poplars of either larch. 



300 MANUAL OF TREE DISEASES 

hemlock or fir has not been proved necessary for the appear- 
ance of the rusts on poplars, although such an association 
of the two required hosts is believed essential for the 
existence of these rusts. If this is true, this rust can be 
avoided by keeping larch, hemlock and fir separated from 
poplars by a distance of several hundred feet. 

Powdery Mildew 

Caused by Uncinula salicis (DC.) Winter 

The powdery mildew of poplar leaves is found throughout the 
United States, but no great damage is done to the tree. It 
occurs also throughout Europe and Asia and over its entire 
range it affects the willows as well. The mycelium grows on 
both sides of the leaves and forms either effused or definitely 
circumscribed white powdery areas. The life histories and 
control of the powdery mildew fungi are similar for all species 
and are discussed in general on page 37. There is apparently 
only this one powdery mildew found on poplar. Some kinds 
of trees are affected by two or more species. 

Yellow Leaf-Blister 

Caused by Taphrina aurea Fries 

The leaves of several species of poplar are affected by the 
yellow leaf-blister. In Europe the black poplar is affected. 
The size of the blisters may vary from very small to an inch in 
diameter. They are yellow at a certain stage in their develop- 
ment, due to the fruiting-structures of the causal fungus. Later 
the color of the blisters changes from yellow to brown. The 
mycelium of the fungus is confined to the space it makes for 
itself between the cuticle and epidermal cells, usually of the lower 
side of the leaf. No branches of the mycelium enter the leaf- 



POPLAR DISEASES 301 

tissue, but the parasitic effects of the fungus exert a stimulus 
which results in an increase in number and size of the mesophyll 
cells of the leaf, causing the blister. The mycelium is not peren- 
nial and new infections are caused by the spores which are 
produced on the surface of the blister and winter-over. 

Catkin-Deformation 

Caused by Taphriiia Johansonii Sadebeck 

The fertile catkins of different species of poplar are affected 
in similar manner as those of alders (see page 87). The 
elements of- the catkin become larger than normal and at a 
certain stage are covered by the yellow fruiting-structures of 
the causal fungus. 

Canker 

Caused by Dothichiza populea Sace. and Briard 

This canker of black or Lombardy poplar and the common 
Cottonwood has recently been found destructive in nurseries 
and on large trees planted for shade and ornament. The 
disease was first reported and studied in Europe, where it is 
known to be especially destructive to the cottonwood in 
France and Italy. It has now been found in the United 
States in New Hampshire, INIassachusetts, New Jersey, New 
York, Pennsylvania, Delaware, INIaryland, Ohio and New 
Mexico. 

Apparently it originated in nurseries in this country which 
have imported the ornamental Lombardy poplar, and from these 
centers diseased trees have been shipped to various regions, 
thus distributing the fungus. Since the disease has only re- 
cently been discovered and because of its destructiveness could 
hardly have been overlooked previously, it seems certain that 
the causal pathogene has been newly imported and is just 
beginning to show its potentialities in this country. Its 



302 MANUAL OF TREE DISEASES 

seriousness in the native poplar stands is yet to be determined. 
The large number of trees killed in nurseries and the serious 
effects produced on recently planted or old established trees 
around the nurseries point to the possibility that this disease 
may assume an epiphytotic nature. 

Symptovis. 

Trees recently transplanted and young nursery trees are 
most seriously affected. Older and well-established trees 
resist the disease to some extent and the cankers develop more 
slowly. The cankers occur on the trunk, limbs and small 
twigs. The diseased bark is slightly sunken and somewhat 
darker in color than the healthy bark. Cankers are commonly 
found around the base of twigs and limbs. The inner bark- 
tissues and cambium are killed and these dead tissues are brown. 
The canker enlarges rapidly and finally may girdle the trunk 
or limb. Small raised pustules are formed on the diseased 
bark. A hole is evident in the top of each pustule and from 
this hole long twisted brown or cream-colored tendrils of 
spores are pushed out. On the trunks and limbs of old trees, 
the cankered area of bark falls away, leaving the bare wood 
surrounded by callus. 

The general effect of the disease on the trees is the killing 
of the twigs and smaller limbs and the disfiguring of the trunk 
and large limbs by the formations of open wounds. Suckers 
are developed from below the cankers, causing an ill-formed 
tree. Thus, while only the younger trees are killed outright, 
the older ones are made useless as ornamentals. In the forest 
the continued activities of such a fungus might constitute a 
menace to the successful production of commercially valuable 
trees, by interfering with the normal healthy development of 
the older trees and preventing the natural reproduction from 
reaching maturity. As yet, however, this disease has not been 
reported in the forests on the timber poplars. 



POPLAR DISEASES 303 



Cause. 



The poplar canker is caused by the fungus Dothichiza populea, 
which has apparently not previously existed in this country. 
It is supposed to have been brought into the United States on 
affected nursery stock from France or Italy where it is common. 
An Italian investigator has proved that this fungus has an as- 
cospore stage which is called Cenanqium populneum Rehm. 
So far, this ascomycetous fungus has not been associated with 
the poplar canker in this country, although it is supposed to 
have been present here as a saprophyte for many years. The 
Dothichiza stage on the cankers is a pycnidial stage. The spores 
which appear temporarily glued together in the spore-tendrils, 
pushed out from the pustules on the diseased bark, are probably 
mainly disseminated by the rain. Also birds and various 
animals which come into contact with the tendrils may carry 
the spores on their bodies. This disease is similar in many 
respects to the Endothia canker of chestnut (see page 140). 

Control. 

Trees from nurseries may bring this disease into new locali- 
ties. Care should be taken to eradicate all dead and cankered 
twigs from stock recently obtained from nurseries. In case the 
disease appears on older trees, pruning off the diseased limbs and 
cutting out the cankered area are the only control measures 
known. For directions for carrying out these types of eradica- 
tion measures, see page 345. 

References 

Hedgeoek, G. G., and Hunt, N. R. Dothichiza populea in the United 

States. Mycologia 8 : 300-308, pis. 194-195. 1916. 
Voglino, Piero. I nemici del Pioppo canadense di Santena. Nemici 

vegetale. Ann. R. Acead. Agr. Torino. 53 : 325-377, figs. 1^. 

1911. 
Delacroix. Georges. Une maladie du Peuplier de la Caroline. Bui. 

Soc. Mycol. France 22:239-252, pi. 1. 1906. 



304 



MANUAL OF TREE DISEASES 



Limb-Gall 

Caused by Bacterium tumefaciens E. F. Smith and Townsend 

Poplar is only one of the many kinds of woody and her- 
baceous plants affected by this gall. The disease occurs 
commonly on fruit-trees, roses, daisies, beets and many other 
kinds of cultivated and wild plants. The over-growth in the 




Fig. 57. — Limb-galls on poplar. 



affected plant-tissue assumes different characters and the 
disease is variously known as: crown-gall, limb-gall, crown- 
knot, root-gall, hairy-root and woolly-knot. In general it is 
called the plant-cancer. Many trees are commonly found with 



POPLAR DISEASES 305 

limb-galls of various sizes (Fig. 57). No definite proof is 
available whether or not these various galls are due to the 
plant-cancer bacterium. Galls have been produced, however, 
on poplar limbs artificially and the organism has been isolated 
from galls on poplar occurring in nature. The galls are hard, 
woody structures variable in size. The surface is rough and 
covered with small knobs of tissue. The causal organism is 
a species of bacterium. Little is known of its life history, so 
far as its dissemination and resting stages are concerned outside 
the host plant. The effect of the organism on the plant-tissue 
has been made the subject of classical studies which have 
revealed many interesting analogies to human cancer. 

References 

Smith, E. F., Brown, N. A., and Townsend, C. O. Crown-gall of 

plants : its cause and remedy. U. S. Dept. Agr. Bur. PI. Jnd. 

Bui. 213 : 3-215 ; pis. 1-36, figs. 1-3. 1911. 
Smith, E. F., Brown, N. A., and McCulloch, L. The structure and 

development of crown gall : a plant cancer. U. S. Dept. Agr. 

Bur. PI. Ind. Bui. 255 : 3-60, pis. 1-109, figs. 1-2. 1912. 

Common White Wood-Rot 

Caused by Fomes igniarius Fries 

White wood-rot caused by the false-tinder fungus (F. igni- 
arius) is the most common wood-rot disease of deciduous 
trees. It is the cause of enormous losses in hardwood forests 
because of the destruction of the timber of the trees. Since 
also the sap wood may be aft'ected, it becomes an equally im- 
portant disease of valuable individual trees. It does not 
seem, however, to be very common outside of the forest areas 
and does not equal in importance the brown checked wood-rot 
in the relative damage caused to shade and ornamental trees. 
The following kinds of trees are known to be aft'ected by the 
common white wood-rot : beech, poplar, willow, maple, birch, 

X 



306 



MANUAL OF TREE DISEASES 



butternut, walnut, hickory and oak. Its range of hosts is 
larger than any other wood-rotting fungus and its distribution 
is limited only by the combined range of its hosts, for it is 
found on all the continents of the world and occurs from 




Fig. .58. — Commou white wood-rot in maple, with a young fruiting-body of 
the causal fungus at the right. 

tropical regions far into colder arctic zones, both to the 
north and south. 

In Europe it is the most common disease of the oak and the 
most dangerous wood disease of fruit-trees of the genera Pyrus 
and Prunus. In this country beech, poplar and oak are the 
most commonly and destructively affected. Fruit-trees, es- 



POPLAR DISEASES 



307 



pecially apple, are often attacked when orchards are near 
forested areas. The maples, especially striped and silver, 
are commonly attacked when mixed in the forest with beech 
and aspen. Trees of all ages become infected and it is not 
uncommon to find ninety per cent or more of second growth 
trees less than five inches in diameter severely decayed. The 
form of the fruiting-bodies and the characters of the decay are 
similar for all the kinds of trees affected. 

Symptoms. 

Cross-sections of limbs or trunks affected by the common 
white wood-rot show that the decay starts in the center of the 
heartwood and gradually extends outward toward the sap- 
wood. The outline 
of the decayed area 
is never regular and 
certain annual rings 
are invaded on one 
side before they are 
on the other. The 
decayed wood is 
soft and whitish, 
with but few cracks 
or fissures. Numer- 
ous narrow and 
more or less con- 
centrically arranged 
black lines are com- 
mon in the decayed 
area. Bordering the white rotted area is a continuous black 
line with a dark-colored zone between it and the normal 
wood (Fig. 58). The black line marks the region of greatest 
activity of the advancing mycelium in converting the normal 
wood into the soft white product of decay. The sapwood and 




jj^iK^^" 



Fig. 59. — Fruiting-body of Fomcs igniarius. 



308 



MANUAL OF TREE DISEASES 



bark are invaded by the mycelium and the living tissues are 
killed. 

Fruiting-bodies of two kinds are formed by the causal fungus. 
They are sometimes considered as two separate species. One 
form is distinctly hoof-shaped with a jet-black and ex- 
tremely checked, charcoal-like upper surface (type of Fovies 
igniarius, Fig. 59), while the other is more shelf-like, with 
the gray to black upper surface marked with concentric arched 




Fig. 60. — Fnnting,-hody of Fomes igniarius. This form 
is sometimes called Fames nigricans. 

ridges and is slightly checked (type of Fovies nigricans, 
Fig. 60). The under surfaces of both types of fruiting-bodies 
are identical, being reddish brown and velvety. The open 
ends of the spore-bearing tubes show as minute circular open- 
ings, barely visible to the unaided eye. The fruiting-bodies 
form at branch stubs which have not healed over. A new 
layer of tubes is added each year and large fruiting-bodies of 
this fungus have been found which showed eighty layers of 
tubes. When the fruiting-body is broken, the layer of tubes 
is seen to be stuffed with white material (Fig. 61). 



POPLAR DISEASES 



309 



Caiise. 

The common white wood-rot of deciduous trees is caused by 
the fungus Fomes igniarius (= Fomes nigricans). The spores 
from the tubes on the 
under surface of the 
sporophores are wind- 
blown and cause infec- 
tion through branch 
wounds where heart- 
wood is exposed. The 
mycelium delignifies the 
wood elements and 
partially destroys the 
cellulose. For a more 
detailed discussion of 
the life history and con- 
trol of the wood-rot 
fungi of living trees, 
see page 64. 




Fig. 61. — Lengthwise section through 
fruiting-body of Fomes igniarius. 



References 

Schrenk, Hermann von, 

and Spaulding, P. 

White heart-rot 

caused by Fomes igniarius. In Diseases of deciduous forest trees. 

U. S. Dept. Agr. Bur. PI. Ind. Bui. 149 : 25-37, pis. 1-3. 1909. 
Schrenk, Hermann von, and Spaulding, P. Heart-rot caused by Fomes 

nigricans. In Diseases of deciduous forest trees. U. S. Dept. 

Agr. Bur. PL Ind. Bui. 149 : 42-44. 1909. 
Atkinson, G. F. Polyporus igniarius. In Studies of some shade tree 

and timber destroying fungi. Cornell Univ. Agr. Exp. Sta. Bui. 

193 : 214-222, figs. 71-79. 1901. 
Hartig, R. Polyporus igniarius Fr. In Die Zersetzungserscheinungen 

des Holzes etc., pp. 114-123, pis. 15-16. 1878. 
Hesler, L. R., and Whetzel, H. H. White heart-rot. In Manual of 

fruit diseases, pp. 72-76, "figs. 20-21. 1917. 



310 MANUAL OF TREE DISEASES 

White Pocket Heartwood-Rot 

Caused by Polyporus Rheades Fries ( = Polyporus dryophilus Berkeley) 

This heartwood-rot is sometimes found in poplar, especially 
in the Northwest, following the common white wood-rot caused 
by Fomes igniarms (see page 305). In oak this heartwood- 
rot is common and destructive in the Southwest. The rot is 
confined to the upper part of older trees and may involve the 
sapwood. In cross-sections of affected poplars, the spring- 
wood of the annual rings is whitish while the summer-wood is 
light brown. The medullary-rays also become white. In 
longitudinal section these white bands of decayed tissue cause 
a mottled appearance. Small irregularly shaped brown areas 
appear here and there. The white areas enlarge until but 
little brownish wood remains between them. No cavities are 
formed since the white delignified fibers are not entirely de- 
stroyed. The sporophores of the causal fungus are shelf- or 
hoof-shaped when they occur at branch wounds and are more 
or less globose when formed directly on the bark. They are 
brown and have a granular sandstone-like core which reaches 
back into the sapwood. For further details concerning this 
heartwood-rot, see under oak diseases, on page 250. 

White Butt-Rot 

Caused by Fomes applanatus Fries 

The fungus which causes this important white butt-rot of 
many kinds of deciduous trees is the most common bracket- 
fungus growing everywhere on dead wood. It is the most 
generally known of the polypores because of the practice 
of using the under surface of the sporophore for amateur 
etching. Recently it has been learned that this fungus attacks 
the wood of the roots and base of many trees, especially poplar, 
beech, oak, birch and maple. The amount of damage caused 



POPLAR DISEASES 311 

by this rot is considerable in some regions, but is in no degree 
related to the general prevalence of the fungus. While found 
everywhere throughout the United States, only occasional 
living trees are attacked over most of its range. Outside of the 
forest, oak and poplar seem to be the most often attacked. 
The heartwood of the roots and the base of the trunk is decayed. 

Symptoms. 

The heartwood is decayed rapidly by the fungus and some- 
times the sapwood is invaded when conditions are favorable 
for its growth. The decayed wood appears only a little lighter 
in color than the normal and retains its woody character. 
It resists cutting with a knife more than its appearance and 
light weight would indicate. Bordering the decayed wood 
at the center of the tree, in beech at least, is a broad dark 
colored zone, a quarter of an inch or more wide. In this dis- 
colored zone the process of decay seems to progress rapidly, 
for just inside this area the decayed wood is of the same char- 
acter as further toward the center of the tree. When split 
lengthwise and smoothed with a knife, the decayed wood shows 
peculiar horizontal markings lighter in color, which at first 
may be mistaken for the tunnels of wood-boring insects, filled 
with mycelium (Fig. 12, page 109). They are, however, simply 
long definite channels in which the wood is reduced to a stage 
at which the fibers are only loosely held together and mixed with 
an abundance of mycelium. This loose completely decayed 
wood can easily be picked out, leaving empty crooked tunnels 
about an eighth of an inch wide and an inch or two in length. 

The sporophores are perennial and are typically almost flat 
to convex. The upper surface is smooth, horny, light to dark 
gray and marked with rather distinct concentric folds represent- 
ing as many years' growth. The under surface is almost white 
and covered with minute pores which are the open ends of long 
perpendicular tubes which bear the spores over their inner 



312 MANUAL OF TREE DISEASES 

surface. When fresh and soft, the lower surface turns brown 
when bruised. When broken the inner substance is found to 
be rusty brown and punky, with a distinct stratification of the 
annually formed layers of tubes. A thicker and more ungulate 
form with a black checked top and thin margin and a slightly 
concave under surface is commonly found growing from wounds 
in the base of living oak trees. This form, while being classi- 
fied under the same name as the typically flat sporophore, 
differs greatly from it in general appearance and may represent 
a closely related species or at least a distinct variety. 

Cmise. 

White butt-rot of poplar, oak, beech and other deciduous 
trees has been found to be caused by the bracket-fungus, Fomes 
applanatiis. Sporophores are formed near the base of the tree 
at wounds or on exposed roots. The fruiting-bodies are peren- 
nial, a new layer of tubes being formed on the under surface 
each year. Infection seems to occur, usually, near the base of 
the tree and the decay does not extend very far up into the trunk. 
Trees in moist situations seem to be more often affected than 
those on drier land. A general discussion of the life history 
and control of the wood-rotting fungi will be found on page 64. 

References 

Heald, F. D. A disease of the cottonwood due to Elfvingia megaloma. 

Nebraska Agr. Exp. Sta. Ann. Rept. 19 : 92-100, pis. 1-4. 1906. 
Hedgcock, G. G. Notes on some diseases of trees in our national 

forests. IV. Phytopathology 4 : 181-188. 1914. 



CHAPTER XXIX 
SPRUCE DISEASES 

Six or more species of spruce (Picea) grow as forest-trees in 
the United States. They are important timber-trees and occur 
most abundantly in the northern states, although their range 
extends southward in the mountains to North CaroHna, Ten- 
nessee, Colorado and California. Spruce is also extensively 
used as an ornamental. 

Several diseases cause damage to spruce in the forest. The 
most important disease aflPecting these trees is the pecky wood- 
rot. Red-brown sapwood-rot and other diseases of the wood 
are also important. Several rust-fungi attack the leaves, 
twigs and cones of spruce. Two of the rusts cause witches'- 
brooms. Other minor diseases cause more or less loss in different 
sections of the country. As an ornamental, spruce is usually a 
healthy tree. 

Seedlin.g Twig-Blight 

Caused by Ascochyta piniperda Lindau 

This blight has been a common source of loss in seed-beds in 
Europe for many years but has only recently been reported in 
this country. It is known to occur in North Carolina on white 
and red spruce seedlings. INIore or less severe damage to 
seedlings of Norway and Sitka spruce are reported from Ger- 
many, Russia and Austria. It is also proved that a disease 
of the twigs of older spruce trees in the forest in Europe is 
caused by the same fungus. On both seedlings and older trees, 
this disease is sometimes confused with frost-injury which it 

313 



314 MANUAL OF TREE DISEASES 

resembles. One of the main differences noted in the field which 
will distinguish this blight from frost-injury (see page 12) is 
that not all the twigs of a given tree are uniformly affected. 
Also the more or less definitely affected areas in the seed-bed 
point to its spread from an original center of infection. Al- 
though this disease has not been found in this country on older 
trees, the symptoms are included in this discussion and are 
not materially different from the effect produced in seedlings. 

Symptoms. 

The blight becomes apparent in seedlings and on older spruce 
trees early in the spring while the tissues of the rapidly growing 
shoots and new leaves are succulent. Infection may take 
place at any point in the new growth, usually at some distance 
back from the tip. The affected area of the shoot turns brown 
and shrivels and the leaves die and fall off. The shoot is 
weakened at the point of infection and the weight of the still 
healthy tip causes it to bend over. Infection may occur at the 
base of the new shoot and the entire shoot will droop. The 
diseased condition soon advances the entire length of the shoot, 
however, and the leaves are shed. The course of the disease is 
confined to the period of two or three weeks after the new growth 
is completed. Small black pustules break through the dead 
bark or appear at the leaf-scars during the summer. 

Cause. 

Twig-blight of spruce is caused by the fungus Ascochyta 
piniperda, formerly called Septoria parasitica. Only the conidial 
stage is known and this appears on the dead twigs. The spores 
are formed in the black fruiting-bodies mentioned above. Pre- 
sumably these spores over-winter and produce primary infection 
of the new growth the next spring. Some ascospore stage may 
be expected to be found on the dead needles or cast-off twigs on 
the ground and these spores may also function in carrying the 



SPRUCE DISEASES 315 

fungus over the winter. The spores seem to be able to infect 
only the young succulent growth, since no new infections occur 
after the shoots have attained full growth. The mycelium 
invades the tissues of the twig and leaves. 

Control. 

No definite measures of control are suggested. It would be 
difficult to keep the new growth covered with any spray mixture 
during its susceptible period, since the rapid growth that is 
made in early spring would expose much new tissue between 
applications. However, some benefit may be derived from 
pulling and burning immediately all diseased trees in the seed- 
bed, as soon as they are noticed. This would prevent to a 
large measure the further spread that season and would eliminate 
the material which would otherwise harbor the fungus until 
the next season. 

References 

Graves, A. H. Notes on diseases of trees in the southern Appalachians 
III. Phytopathology 4 : 63-72, pi. .5. 1914. 

Hartig, R. Septoria parasitica, the spruce-shoot disease. In Text- 
book of the diseases of trees, pp. 143-146, figs. 81-82. 1894. 

Leaf Blister-Rusts 

Caused by Melampsoropsis cassandrce (Peck and Clinton) Arthur, 
_ M. abietina (Alb. and Schw.) Arthur, and M. ledicola (Peck) Arthur 

The leaves of red, black, white, Engelmann and Sitka spruce 
throughout the range of these trees in the United States are 
commonly afl^ected by one or more of three very similar needle 
blister-rust diseases. All three of the causal rust-fungi have 
the alternate stages of their life history on plants of the heath 
family, principally on Labrador tea, bog rosemary and leather- 
leaf. The whitish blisters formed on the under sides of the 
spruce needles shed spores (oeciospores) which infect the heaths. 
On these plants, small reddish or yellowish pustules bearing the 



316 MANUAL OF TREE DISEASES 

urediniospores develop. Later in the autumn small bright 
red or yellowish clumps of teliospores are formed on the leaves 
and these spores over-winter and produce basidiospores in 
the spring. These latter spores infect the young spruce needles. 
The affected needles become yellowish and soon produce two 
irregular rows of white blisters on the under surface. 

The three species of closely related rust-fungi causing these 
diseases were known by the following names for the stage on the 
spruce before the stages on the heath plants were connected 
with them : Peridermium abietinum (Alb. and Schw.) Thiim. 
= M. ahietina (Alb. and Schw.) Arthur ; P. decolorans Peck 
= M. ledicola (Peck) Arthur ; P. consimile Arthur and Kern 
= M. cassandrcB (Peck and Clinton) Arthur. 

References 

Arthur, J. C, and Kern, F, D. North American species of Peri- 
dermium. Bui. Torrey Bot. Club 33 : 403^38. 1906. 

Fraser, W. P. Cultiu-es of some hetercecious rusts. Mycologia 3 : 
67-74. 1911. 

Fraser, W. P. Cultures of hetercecious rusts. Mycologia 4 : 175-193. 
1912. 

Clinton, G. P. Hetercecious rusts of Connecticut having a Perider- 
mium for their secial stage. Connecticut Agr. Exp. Sta. Ann. 
Rept. 1907-1908 : 369-396, pis. 25-32. 1908. 

Leaf-Rust 

Caused by Chrysomyxa Weirii Jackson 

The leaves of Engelmann spruce are affected by a rust disease 
in the Northwest. This leaf-rust differs markedly from the 
blister-rusts of spruce (see page 315). The affected needles 
show yellowish spots on which develop prominent orange or 
brownish waxy pustules which break through the epidermis. 
The teliospores formed in these pustules germinate and produce 
basidiospores which infect other spruce needles. No alternate 
host is required in the life history of this rust and the seciospore 
and urediniospore stages are omitted. 



SPRUCE DISEASES 317 

Brown Felt-Blight 

Caused by Herpotrichia nigra Hartig and H. quinquescptata Weir 

Although this disease has been noted in European literature 
as important on spruce, juniper, larch and mountain pine for 
many years, it is only recently that any mention has been 
made of it in the United States. In this country, as in Europe, 
it is found only at high altitudes from six to eleven thousand 
feet above sea level. So far, it is reported in the northwestern 
states on species of spruce, fir, juniper, cedar (Libocedrus), 
arbor-vitse and hemlock. A similar disease which cannot be 
distinguished as to its symptoms from this one occurs in the 
same region on species of pine. The brown felt-blight of pine 
is caused by a different species of fungus, however, and is 
discussed briefly under pine diseases, on page 271. Both in 
Europe and the United States, the damage caused by this 
blight is considerable and young trees and the lower branches of 
older trees suffer most, although in some localities entire stands 
are badly affected and have the general appearance of having 
been swept by fire. Even when the damage is not so severe, 
the annual increment of wood is lessened and the general health 
of the trees impaired. 

Symptoms. 

A brown felt-like mass of mycelium spreads extensively over 
the leaves and twigs, causing them to become matted together 
and completely covered (Fig. 16, page 131). In the case of 
young trees, all the foliage may become covered. The lower 
branches of older trees are more commonly affected than the 
upper part. The mycelium enters the leaf-tissue and the leaves 
are killed through the combined action of the internal food- 
gathering mycelium and the thick covering over the leaves 
which shuts out the light and produces a high humidity. The 
mycelium may pass from one tree to another where branches 



318 MANUAL OF TREE DISEASES 

touch each other. Small fruiting-bodies of the fungus causing 
the disease are found buried in the felt of mycelium. 

Cause. 

Three different species of fungi cause brown felt-blight of 
conifers, namely : Herpotrichia nigra, common to Europe and 
the United States on various conifers, except pines ; Herpo- 
trichia quinqueseptata, newly described on spruce in the North- 
west; and Neopeckia Coulteri, found only on species of pines. 
The effect of all three species is similar and they cannot 
be distinguished except by microscopic examination of the 
spores. 

The life history of these fungi is interesting. Only one 
spore stage is known. The fruiting-bodies (perithecia) are 
buried in the felt of mycelium and contain ascospores. The time 
of infection is not definitely known but young seedlings and the 
lower limbs which are buried in snow most of the winter are 
the most generally affected parts. Whether infection takes 
place under these conditions is a matter of conjecture. The 
mycelium spreads very rapidly during the summer. A case 
is described in which a branch of Alpine fir was entirely covered 
by the growth of mycelium in a single season. The mycelium 
enters the leaves and marked changes are brought about in the 
mesophyl-tissue. An abundant growth of external mycelium 
is also produced which covers the entire surface of the leaves 
and twigs and binds them together into a mass. By the advance 
of this epiphytic growth of mycelium over the surface of healthy 
needles, it is possible that the fungus brings about humidity 
relations which make possible the infection of the leaf and the 
development of the internal feeding mycelium. Thus after 
obtaining its start in a few needles buried in the snow, this fungus 
may in this way prepare its own conditions for infection and 
cause physiological changes in the leaves which render them 
more susceptible. 



SPRUCE DISEASES 319 

References on Brown Felt-Blight 

Sturgis, W. C. Herpotrichia and Neopeckia on conifers. Phytopa- 
thology 3 : 152-158, pis. 12-13. 1913. 

Hedgcoek, G. G. Notes on some diseases of trees in our national 
forests. IV. Phytopathology 4 : 181-188. 1914. 

Weir, J. R. A new leaf and twig disease of Picea engelmanni. Jour. 
Agr. Res. 4 : 251-253, pi. 34. 1915. 

Leaf- and Twig-Blight 

Caused by Pestalozzia funcrea Desm. 

A blighting of the leaves and twigs of spruce, pine and hemlock 
in the nursery and occasionally of slightly older trees is often 
ascribed to species of Pestalozzia. In most cases the symptoms 
resemble somewhat those described under seedling twig-blight 
caused hy Ascochyta pinipcrda (see page 313). Infection occurs 
in the early spring when the new twigs are developing. Both the 
needles and stems are invaded by the mycelium and killed. The 
entire seedling plant is killed while on older trees the current 
growth only is affected. The spores of Pestalozzia funerea are 
often definitely associated with these blight symptoms. The 
spores are pushed out through openings in tlie bark either as 
cylindrical or flattened horn-like masses. Artificial inocula- 
tions have proved this species of Pestalozzia to be parasitic 
under conditions of high humidity. 

References 

Wenner, J. J. A contribution to the morphology and life history of 

Pestalozzia funerea Desm. Phytopathology 4 : 375-384, pi. 27, 

figs. 1-7. 1914. 
Spaulding, P. A blight disease of young conifers. Science 26 : 220- 

221. 1907. 
Hartley, C. Pestalozzia needle blight. In The blights of coniferous 

nursery stock. U. S. Dept. Agr. Bui. 44 : 15-16. 1913. 
Graves, A. H. Notes on diseases of trees in the southern Appalachians 

III. Phytopathology 4 : 63-72, pi. 5. 1914. 



320 MANUAL OF TREE DISEASES 

Cone-Rust 

Caused by Melampsoropsis pyrolce (DC.) Arthur 

, The young green cones of spruce are sometimes attacked by 
this rust-fungus which occurs very commonly throughout 
northern United States on species of wintergreen. The cones 
of black, red, white and Engelmann spruce have been found 
affected in northeastern United States and in Colorado. The 
wide distribution of the same fungus on its other host, the 
wintergreen, signifies, however, that it may be expected to occur 
anywhere in northern United States from the Atlantic to the 
Pacific. It is common in Europe also. Basidiospores from 
over-wintering teliospores on the leaves of wintergreen infect 
the green scales of the young cones in the spring and a few 
weeks later roundish, whitish blisters burst through the epidermis 
of the affected scales. Spores (aeciospores) from these blisters 
infect the leaves of wintergreen. The under surfaces of the 
wintergreen leaves are often densely covered with the reddish 
pustules of the urediniospores. The fungus can live over in 
the persistent leaves of the wintergreen and thus the life history 
may be carried on without the stage on the spruce cones. 

References 

Fraser, W. P. Cultures of heteroecious rusts. Mycologia 4 : 175- 

193. 1912. 
Arthur, J. C, and Kern, F. D. North American species of Perider- 

mum. Bui. Torrey Bot. Club 33 : 403-438. 1906. 

Rust Witches'-B rooms 

Caused by Peridermium coloradense (Dietel) Arthur and Kern, and P. 
boreale Arthxu* and Kern 

These rust diseases, which often result in large witches'- 
brooms, are common in the mountain regions of central western 
and northwestern United States on Engelmann and Colorado 



SPRUCE DISEASES 321 

blue spruce. The first species of fungus mentioned above is 
also found on black spruce in the northeastern states. The 
mycelium is perennial in the twigs of the spruce and they are 
dwarfed. Two irregular rows of whitish or slightly pinkish 
blisters are formed in early spring on the under sides of the 
needles of the affected twigs and brooms. Although it is ex- 
pected that these fungi have another stage in their life history 
on some flowering plant, this has as yet not been discovered. 

Reference 

Arthur, J. C, and Kern, F. D. North American species of Perider- 
mium. Bui. Torrey Bot. Club 33 : 403-438. 1906. 

Mistletoe Witches'-Broom 

Caused by Razoumofskya pusilla (Peck) Kuntze 

This species is the only member of either the dwarf or leafy 
mistletoes that grows in northeastern United States. It occurs 
on black, red and white spruce and has been found once causing 
a witches'-broom on eastern larch in Vermont. It is only seen 
occasionally on the red and white spruce but is more or less 
common on black spruce. When the parasite occurs, the spruce 
is frequently killed or at least dwarfed to half its normal size 
and makes very irregular growth. 

SymptoTus. 

Two types of symptoms are noticeable on black spruce. 
The weaker and more shaded branches when attacked make an 
abnormal growth in length and the branches are more spread- 
ing. The foliage of these branches is yellowish and the leaves 
much smaller than normal. The usual symptom, however, is 
the production of upright clumps of branches, known as witches'- 
brooms (Fig. 62). A lateral branch near the infected part 
assumes an upright growth. Around the base of this branch 

Y 



322 



MANUAL OF TREE DISEASES 



many upright laterals arise and in time large brooms are 
formed. The foliage of the brooms is yellowish and the leaves 
smaller than normal. The ultimate effect of the production of 




Fig. 62. — Witches'-broom on black spruce 
caused by a dwarl mistletoe. 



several brooms, even on an older tree, is slow starvation of the 
remainder of the tree. As shown in the illustration (Fig. 63), 
the tree finally dies, the brooms being the last part to succumb. 



SPRUCE DISEASES 



323 



The mistletoe plant is very small. It is usually less than a 
half inch tall but may grow as large as one inch. The pollen 
and seed are produced 
on separate plants which 
usually grow on different 
trees. The plants con- 
sist of a short stem 
with appressed scale-like 
leaves. They are either 
yellowish or dark colored. 

Cause. 

The witches'-broom of 
spruce is caused by the 
dwarf mistletoe, Ra- 
zoumofshya piisilla. The 
floral organs of the plant 
are mature in early spring 
and the seeds are ready 
to be disseminated in 
September. Before the 
seeds are discharged, the 
plants bend toward the 
tip of the branch. In 
this position the seeds 
are forcibly projected and 
being sticky they adhere 
to the younger twigs on 
which they may lodge. 
Rootlets are sent into 

the bark and wood of Fig. 63. — Mistletoe witches'-brooms on 

the twig and a parasitic ^^^^^ spruce. Tree almost dead. 

relation established. The increased growth of the branches 
and the formation of the witches'-brooms are due to the 




324 MANUAL OF TREE DISEASES 

stimulus which the parasite causes in the tissues. For a 

further discussion of the mistletoes which grow parasitic on 

trees, see page 54. 

References 

Schrenk, Hermann von. Notes on Arceuthobium pusillum. Rhodora 

2 : 2-5, pi. 12. 1900. 
Jack, J. G. Arceuthobium pusillum in Massachusetts. Rhodora 

2 : 6-8, pi. 13. 1900. 
Jones, L. R. Arceuthobium pusillum on a new host in Vermont. 

Rhodora 2 : 8-9, pi. 14. 1900. 

Pecky Wood-Rot 

Caused by Trametes pini Fries 

Spruce is commonly affected by pecky wood-rot or ring- 
shake. This disease is the most destructive wood-rot of coni- 
fers in the United States. It has been reported in larch, pine, 
spruce, hemlock, fir and arbor-vitse. Practically all conifers 
seem to be susceptible except the junipers. In Europe, pine, 
larch, fir and spruce are attacked. The usual common name 
for this disease is ring-shake, because a few annual rings are often 
destroyed, a part of the distance or entirely around the trunk, 
causing a shake in the timber. This symptom is not so com- 
mon in those conifers with a low resin-content, however, and 
the name pecky wood-rot seems more appropriate. It is by 
far the most destructive disease of conifers in the forest and 
by some is believed to equal in importance all other wood- 
rots. The sapwood and bark as well as the heartwood are 
invaded and decayed. 

Symptovis. 

The appearance of spruce heartwood when decayed by this 
fungus is characteristic and the rot may be identified without 
the accompanying sporophores. Around the decayed area, the 
spruce wood is stained a purplish tinge. In cross-section when 



SPRUCE DISEASES 325 

smoothed with a knife or plane, the wood inside the purple 
zone is found to be full of small holes or pockets with white 
linings (Fig. 64). Narrow black lines are sometimes present 
between the pockets. The partially decayed wood between 
the pockets is reddish in color. If the affected wood is split, 
the pockets are found to be longer than wide and the white 
fibers contained and the black lines between the pockets can 





//. 



Fig. 64. — Pecky wood-rot in spruce. 

be more clearly seen (Fig. 65). The decay extends eventually 
into the sapwood and bark. 

Trees affected by this disease, as is the case with other wood- 
rots, do not show any external symptoms until the sporophores 
appear and limbs cr the top of the tree die due to the girdling 
action when the sapwood is destroyed. The sporophores are 
of two types, depending on the place from which the mycelium 
emerges in its formation. A triangular-shaped shelving form 
is produced at old branch wounds, where the food materials 
gathered from an extensive region are furnished for the forma- 
tion of a single fruiting-body. At other places where the 
mycelium has reached the sapwood and bark, a large number of 
small fruiting-bodies are formed which lie closely appressed to 
the bark and only project slightly at the upper edge. The larger 
sporophores from branch wounds add a new layer of tubes each 
year. The upper surface is hard, black and roughened by 



826 



MANUAL OF TREE DISEASES 



many irregular concentric folds. The under surface is light 
brown and covered with minute holes which are the open ends 
of the tubes in which the spores are borne. 

Caiise. 

Pecky wood-rot of conifers is caused by the bracket-fungus 
Trametes pini. This name was first applied to the shelving 
form of sporophore and later the smaller resupinate form was 




Fig. 65. — Advanced stage of pecky wood-rot in lougituJiiial section. 

named Trametes pini abietis. This latter name is no longer 
used, since the identity of the two forms has been established. 
Like other fungi of the same group, the spores are formed in 
perpendicular tubes on the under side of the sporophore. The 
spores drop out of the tubes and are disseminated by the wind. 
Infection may occur when these spores lodge on exposed heart- 
wood, at broken branches or when the top of the tree is 



SPRUCE DISEASES 327 

broken. The tree is relatively immune in the earlier stages 
of growth before heartwood is formed, since wounded sap- 
wood is largely protected by the resinous substances which 
are exuded. Infection may also occur by the fungus ex- 
tending down into the roots and passing into healthy trees 
where a natural grafting of the roots has taken place. For a 
more detailed discussion of the life history and control of 
the wood-rot fungi, see page 64. 

References 

Schrenk, Hermann von. Trametes pini (Brot.) Fr. forma abietis 

Karst. In Some diseases of New England conifers. U. S. Dept. 

Agr. Div. Veg. Phys. and Path. Bui. 25 : 31-40, pis. 6-9. 1900. 
Atkinson, G. F. Trametes abietis. In Studies of some shade tree 

and timber destroying fungi. Cornell Univ. Agr. Exp. Sta. 

Bui. 193 : 227-235, figs. 83-90. 1901. 
Hedgcoek, G. G. Notes on some diseases of trees in our national 

forests. II. Phytopathology 2 : 73-80. 1912. 
Hole, R. S. Trametes pini, Fries, in India. The Indian Forest Records 

5:5: 1-26. pis. 1-8. 1915. 
Hartig, R. Trametes pini Fr. In Wichtige Krankheiten der Wald- 

baume, pp. 43-61, pi. 3. 1874. 
Hartig, R. Trametes pini Fr. In Die Zersetzungserscheinungen des 

Holzes, etc., pp. 32-39, pis. 5-6. 1878. 

Red-Brown Sapwood-Rot 

Caused by Fomes pinicola Fries 

This wood-rot of spruce, pine, fir, larch and hemlock is 
common in the forest wherever conifers grow. Trees in poor 
health are more frequently affected. The wood is reduced to a 
red-brown powdery mass, barely held together by anastomosing 
sheets of mycelium. The sporophores of the causal fungus are 
very common on fallen logs and dead standing trees. They are 
conspicuous because of the red varnished margin and cream- 
colored under surface. This disease is discussed more fully 
under fir diseases, on page 165. 



328 MANUAL OF TREE DISEASES 

Stringy Red-Brown Heartwood-Rot 

Caused by Echinodontium tinctorium Ellis and Everhart 

In western United States Engelmann spruce is destructively 
attacked by tliis heartwood-rot. Fir and western hemlock 
are affected by the same disease. When this heartwood-rot 
is present in the tree, it may be identified from the exterior by 
the rusty knots. The heartwood of the branch stubs is colored 
a bright red. Three distinct stages in this decay are recognizable 
when the trees are cut. As the rot advances, the wood becomes 
discolored, spongy and occasionally contains light brown spots. 
Later the wood becomes red-brown and the spring-wood is 
dissolved, leaving the summer-wood of the annual rings in 
separated layers. These sheets of summer-wood are then 
destroyed and the tree is hollow. The fruiting-bodies of the 
causal fungus are large woody bodies with pendent teeth 
on the lower surface. Further details concerning this heart- 
wood-rot will be found under fir diseases, on page 166. 

Brown Pocket Heart^vood-Rot 

Caused by Fomes roseus Fries 

Spruces are often affected by the browm pocket heartwood- 
rot. The same rot is also found in juniper, fir, larch, pine and 
hemlock. When the decay has advanced to its final stage in 
spruce, it may be confused w4th the red-brown root- and butt-rot 
caused by Polyporus Schweinitzii (seepage 331). At first long 
cylindrical pockets of brown charcoal-like wood are formed in 
the heartwood. The pockets, however, increase in size until 
they coalesce and then the wood is uniformly brownish and 
splits into cubes. The fruiting-bodies of the causal fungus are 
either small, thin, shelf-like bodies or large and hoof-shaped. 
The under surface is rose-colored. For further details con- 
cerning this disease, see under juniper diseases, on page 204. 



SPRUCE DISEASES 329 

CuBoiDAL Wood-Rot 

Caused by Polyporus borealis Fries 

This wood-rot occurs in spruce and hemlock. No definite 
statements are found in hterature concerning its importance and 
distribution in this country. The first evidence of the decay 
in the wood is the appearance of fine parallel strands of mycelium 
which burrow holes in the radial and tangential direction. 
Later these strands of mycelium become larger and appear as 
white cords in the wood (Fig. 28, page 186). Finally the 
mycelium disappears, leaving numerous empty channels, and 
the wood splits into minute cubes. For further details con- 
cerning this wood-rot, see under hemlock diseases, on page 185. 

Brown Root- and Butt-Rot 

Caused by Fomes annosus Fries 

Practically all conifers are occasionally affected by the brown 
root- and butt-rot. In Europe this disease is recognized as 
one of the most destructive to conifers in the forest. In this 
country it is found to some extent both in the eastern and 
western forests, but it is not nearly so important as many 
other root and trunk diseases. It occasionally occurs in pine, 
spruce and fir, and may be expected in other conifers, including 
juniper. The fungus causing this root-rot is sometimes found 
on deciduous trees, but is considered both in Europe and North 
America to be of negligible importance and probably never 
parasitic on hardwood trees. The characteristics of the rot 
seem to differ somewhat with the kind of tree affected, but since 
these variations have not been described it is impossible to treat 
them in detail. In the conifers with a low resin-content, the 
decay extends upward in the trunk for several feet. This is 
especially true in the firs of the western forests. In resinous 
conifers, the rot is confined to the roots and butt of the tree. 



330 MANUAL OF TREE DISEASES 

Symptoms. 

The general symptoms of this root- and butt-rot are as 
follows. The mycelium invades the heartwood, sapwood and 
bark of the roots. The most rapid progress is made in the heart- 
wood. The first sign of the rot is a bluish discoloration of the 
wood. The wood then becomes dirty yellow and finally 
brownish or red-brown. While this color change is progressing, 
black spots appear in the spring-wood of the annual rings. 
Rapid decomposition of the fibers around the black spots results 
in white areas with black centers. The white areas then coalesce 
and result in the complete destruction of the spring-wood. This 
leaves the layers of brown and brittle summer-wood as separate 
sheets of tissue. These sheets shrink and, falling apart, cause 
the root to become more or less hollow. While this process of 
destruction is going on in the wood, white sheets of mycelium 
are formed in the bark, which is killed. The same general 
changes are shown in the heartwood of the trunk where the 
amount of resin present does not interfere with the development 
of the mycelium. 

The sporophores of the causal fungus are formed on the roots 
and base of affected trees. They appear as perennial, shelving 
bodies with a light brown upper surface and white or yellowish 
under surface. The inner structure of the bodies is white. 
Small pores are apparent on the under surface. The sporo- 
phores are also often found under the surface of the soil as 
incrusting bodies on the roots and base of the trunk. 

Cause. 

The brown root- and butt-rot of conifers is caused by Fomes 
annosus. The spores from the tubes on the under sides of the 
fruiting-bodies may cause infection through wounds in exposed 
roots or possibly in fire scars and other wounds at the base of 
the tree. The most efficient means of spreading from tree to 
tree is by way of the roots which come in contact with each 



SPRUCE DISEASES 331 

other in the soil. No strands of mycelium grow through the 
soil, however, as in the case of the shoe-string root-rot (see 
page 78). For further details concerning the life history 
and control of wood-rotting fungi, see page 64. 

References 

Schrenk, Hermann von. Polyporus annosus Fr. In Some diseases 
of New England conifers. U. S. Dept. Agr. Div. Veg. Phys. 
and Path. Bui. 25 : 49-50. 1900. (It seems probable that von 
Schrenk also described the rot due to Fomes annosus under the 
discussion of Polyporus siibacidus Pk. on pages 44-49.) 

Hartig, R. Trametes radiciperda R. Hartig. In Wichtige Krank- 
heiten der Waldbaume, pp. 62-65, pi. 3. 1874. 

Hartig, R. Trametes radiciperda. In Die Zersetzungserscheinungen 
des Holzes, etc., pp. 14-31, pis. 1-4. 1878. 

Red-Brown Root- and Butt-Rot 

Caused by Polyporus Schweinitzii Fries 

Spruce, as well as fir, pine, larch, hemlock and arbor-vitse, 
is commonly affected by this root-rot throughout its range. 
This disease is second only in importance to the pecky wood- 
rot. The sapwood is at first yellowish and cheesy but later 
becomes red-brown and brittle. The sporophores are stalked 
reddish-brown umbrella-like structures. For a more complete 
description of this rot see under pine diseases, on page 294. 

Yellow Root-Rot 

Caused by Sparassis radicata Weir 

This root-rot of spruce is as important as the shoe-string and 
brown root-rots in the Northwest. Fir, pine and larch are 
also affected by the yellow root-rot in the same region. Lateral 
roots even to a considerable depth in the soil are decayed and 
killed. Yellowish fan-like sheets of mycelium are formed in 
the bark. The sapwood is then affected and the medullary- 



332 MANUAL OF TREE DISEASES 

rays destroyed. Later the heart wood is decayed and becomes 
brownish. The fruiting-bodies of the causal fungus are large, 
white, fleshy structures formed on the ground. They are 
attached to the diseased roots by long tuber-like stalks. 
Further details concerning this root-rot will be found under 
fir diseases, on page 170, 



CHAPTER XXX 
SYCAMORE OR PLANE-TREE DISEASES 

The species of sycamore or plane-tree are large trees growing 
abundantly throughout their range in bottom-lands. Although 
not making a part of the forest lands of the country, the wood of 
sycamore is utilized for many specialized products. Three 
species of Platanas are recognized as native to the United States. 
Others are Mexican. A common street tree is P. acerifolia, 
thought to be a hybrid and often passing as P. orientalis, 
which latter is native in Europe and Asia. 

The sycamore is apparently subject to but few important 
diseases. The leaf- and twig-blight, however, causes serious 
damage to the tree wherever it grows. The trees are de- 
formed and although defoliated frequently, are not often killed. 
Several other fungi cause leaf-spots of sycamore. No other 
diseases of importance have been recorded on this tree. This 
may be due partially, however, to a lack of attention to the 
tree, since it is not associated with the principal timber-trees 
and is of little economic importance. 

Leaf- and Twig-Blight 

Caused by Gnomonia veneta (Saec. and Speg.) Klebahn 

The most common and destructive disease of the sycamore 
is the leaf- and twig-blight or anthracnose. Some species of 
oak, especially those belonging to the white and red groups, 
suffer to some extent from the same disease. The disease 
is generally prevalent throughout eastern and central United 

333 



334 MANUAL OF TREE DISEASES 

States and In California. The most severe damage occurs 
where the twig-blight and canker types of the disease seriously 
deform the trees. Although certain trees are more or less 
affected every year, this blight occurs in epiphytotic form in 
seasons when weather conditions are favorable in early spring 
for the development of the causal pathogene. The Oriental 
plane and oaks in Europe, where they are extensively used as 

shade and orna- 
mental trees, are 
attacked by the 
same fungus. It 
is probable that 
the range of this 
fungus is coexistent 
with the distribu- 
tion of the syca- 
more and it may be 
expected to cause 
damage wherever 
the tree is grown. 
Owing to repeated 
defoliation, several 
Fig. 66. — Leaf-blight of sycamore. yg^ps in SUCCession, 

and the twigs being killed back, the ultimate damage is con- 
siderable. Cases have been reported in which trees were 
killed outright. Generally, however, repeatedly affected trees 
show great recuperative powers, and produce a second crop of 
leaves year after year. 

Syinptoms. 

Leaf-blight becomes noticeable soon after or while the leaves 
are expanding in the spring. Often some leaves and the grow- 
ing tip of the twig are affected, turn brown and die as they 
emerge from the bud. This symptom is often confused with 




SYCAMORE OR PLANE-TREE DISEASES 



335 



late frost-injury (see page 21). The usual type of lesions, how- 
ever, develops later, as elongate independent brown spots along 
the main veins of the leaf; The diseased condition of the vein 
and adjoining tissues causes the rapid death of the leaf-tissue 
around the original 
spot, resulting in 
larger dead brown 
areas (Fig. 66). 
Two or more such 
lesions finally in- 
volve the entire leaf, 
and the tree, when 
infection has been 
general, appears 
from a distance as if 
scorched. In moist 
weather, small pin- 
head-like, cream- 
colored spots are 
produced on the 
under sides of the 
leaf along the veins 
which are included 
in the dead areas. 
The leaves soon 
drop after being 
killed and often the 
tree is completely 
defoliated and re- 




lu. G( 



Sycamore defoliated by ieaf-blig)it 
fungus. 



mains bare until later in the summer, when new leaves are 
developed (Fig. 67). 

The smaller twigs are also killed and cankers are formed on 
the branches of an inch or less in diameter, sometimes girdling 
them (Fig. 68). At first, the cankered area is sunken with a 



336 



MANUAL OF TREE DISEASES 




slightly raised margin. Small black fruiting-bodies break 
through the dead bark the spring following infection. After a 
year or two the dead bark falls away, leaving the wood bare and 

surrounded by a 
callus (Fig. 69). 
The wounds are 
then often healed 
over and no great 
damage results. 
On the small twigs 
which are killed 
back, minute pim- 
ples cover the yel- 
low bark. The 
repeated killing of 
the twigs causes 
abnormal branch- 
ing and gnarled 
growths which many times produce witches'-brooms. This 
causes the tree to have a general irregular and scraggly appear- 
ance. In the northeastern states, in some localities, it is often 
hard to find trees that are not thus affected. 

Cause. 

Leaf- and twig-blight of sycamore and oak is caused by the 
fungus Gnomonia veneta. The perithecial stage occurs on the 
fallen leaves and matures in the spring. The stage which de- 
velops as the small cream-colored pustules, along the veins of 
the blighted leaves while they hang on the tree, is known as 
Glceosporium nervisequum. Other names were given to the 
spore stages developed on the twigs and cankers before their 
identity as one fungus was proved. There are still many facts 
about this disease to be learned. It is not known which spore 
stage causes the first infection of new leaves in the spring. The 



Fig. 68. — Cankers on small sycamore twigs. 



SYCAMORE OR PLANE-TREE DISEASES 



337 



f 



ascospores from the dead leaves on the ground or conidia from 
the fruiting-bodies on dead twigs or 
cankers may cause the primary infec- 
tion. Internal over-wintering mycelium 
may also grow out into the newdy de- 
veloping twigs and leaves from the in- 
fected twags of the previous year. After 
a few leaves are infected, the spores 
from the fruiting-structures along the 
veins are thought to be largely responsi- 
ble for the general infection of the re- 
maining leaves of the tree. Frequent 
rains and a humid atmosphere are con- 
ducive to epiphytotics of this disease 
when these conditions occur in proper 
correlation w^ith the development of 
the leaves and the first fruiting-bodies 
resulting from primary infection. The 
twigs and branches are infected by the 
spores produced on the leaf-lesions or 
by the mycelium growing down through 
the petioles into the twigs. Twigs in- 
fected the season before are often 
girdled and killed just after the leaves 
expand the next spring. After the 
leaves fall to the ground, the mycelium 
lives saprophytically and produces per- 
ithecia which mature in the spring just 
as the buds are bursting. It is probable that the spores are 
shot out of the perithecium, as is the case with similar fungi. 

Control. 

Since this disease is universally present on sycamore and com- 
mon on oak as w^ell, the first steps in controlling it must begin 
z 



Fig. 69. — Cankers on 
limbs of sycamore. 



338 MANUAL OF TREE DISEASES 

with the elimination of the spore-producing material in the 
vicinity of the tree. All the leaves from affected trees should 
be carefully raked together and burned. Following this, all 
dead or cankered twigs and branches should be pruned from the 
tree and burned. This is a tedious operation and unless care is 
taken many infected twigs will be missed. The twigs that are 
overlooked become apparent as soon as the leaves are out in the 
spring and should be removed at that time. The twigs left 
until that time, however, have had a chance to disseminate 
spores and start the primary infection of the leaves. If these 
sanitation precautions are thoroughly carried out for all the 
sycamores and oaks in the vicinity, the amount of primary in- 
fection may be considerably reduced, or under adverse weather 
conditions entirely eliminated. However, since the greatest 
damage probably comes from secondary infection, spraying with 
bordeaux mixture is advised to protect the leaves. When 
spraying has been tried, this disease has been successfully con- 
trolled. Bordeaux mixture (4-4-50 or 5-5-50) applied thor- 
oughly with a power sprayer, so that all the leaves are covered, 
will prevent the spores that may be present from infecting the 
leaves. The number and time of the applications depend on 
the weather conditions. The first application should be made 
after the buds burst and before the leaves are half grown. A 
second application should be given about one week later and 
the third and fourth if the season is rainy, at intervals of two 
weeks. For fuller directions on spraying trees, see page 357. 

References 

Southworth, E. A. A disease of the svcamore. U. S. Dept. Agr. 

Kept. Com. Agr. 1888 : 387-389, pi. 15. 1889. 
Southworth, E. A. Gloeosporium nervisequum (Fckl.) Saee. Jour. 

Mycology 5 : 51-.52. 1889. 
Edgerton, C. W. The physiology and development of some anthrac- 

noses. Bot. Gaz. 45:367-408, pi. 11, figs. 1-17. 1908. 
Duggar, B. M. Anthracnose of sycamore. In Fungous diseases of 

plants, pp. 278-280. 1909. 



CHAPTER XXXI 

WALNUT DISEASES 

The walnut is commonly attacked by leaf-spot diseases which 
may cause defoliation. The common white wood-rot and the 
brown checked wood-rot sometimes are found in walnut. Com- 
pared with many other kinds of deciduous trees, the walnut is 
rarely affected by important diseases. The native black wal- 
nut is Juglans nigra. The walnut of commerce, usually 
called " English " walnut, is J. regia. Other species are in 
cultivation. 

Leaf-Spot 

Caused by Marssonia juglandis (Lib.) P. Magnus 

This leaf-spot is also common on butternut. The spots are 
irregular in shape and dark brown (Fig. 15, page 123). In some 
seasons these spots become abundant and the leaves fall. This 
leaf-spot is more fully described under butternut diseases, on 
page 123. 

Common White Wood-Rot 

Caused by Fomes igniarius Fries 

The wood of the black walnut is sometimes reduced to a white 
punk by the false-tinder fungus. Beech, poplar, oak and maple 
are commonly affected by the same fungus. The sporophores 
and the nature of the decay are similar for all the kinds of trees 
affected and are described under poplar diseases, on page 305. 

339 



340 MANUAL OF TREE DISEASES 

Brown Checked Wood-Rot 

Caused by Polyporus sulphureus Fries 

The black walnut is at times affected by the brown checked 
wood-rot caused by the sulfur fungus. Oak, chestnut, maple, 
butternut, locust and alder are often affected by the same 
disease. The wood is changed to a reddish charcoal-like sub- 
stance which is split into cubes. These cubes are separated 
from each other by sheets of mycelium. The sporophores of 
the causal fungus are orange and sulfur-yellow and appear in 
late summer. The symptoms are more fully described under 
oak diseases, on page 247. 



CHAPTER XXXII 

WILLOW DISEASES 

The many species of willow (Salix), which are the common 
trees and bushes in lowlands and along stream banks, are not 
subject, so far as known, to many important diseases. A few 
leaf diseases are known which may cause defoliation. The 
leaf-rusts are very common. Wood-rots are often found in 
willow but no studies have been made of them. In general, 
but little attention has been paid to willow diseases because of 
the slight economic importance of the trees. 

Powdery Mildews 

Caused by Uncinula salicis (D.C.) Winter, and Phyllactinia corylea 

(Pers.) Karst. 

Two powdery mildew fungi attack the leaves of willows in the 
United States, Both species are found throughout the country. 
They are of little importance so far as damage to the trees is con- 
cerned. Without the aid of the microscope, the two cannot be 
distinguished from one another. The one, Uncinula salicis, 
however, may occur on both sides of the leaf, while Phyllactinia 
corylea is usually confined to the under side (Fig. 70). The 
black fruiting-bodies of the former are smaller than those of the 
latter. The life history and methods of control of the powdery 
mildew fungi are discussed on page 37. 

Leaf-Rusts 

Caused by fungi of the genus Melampsora 

Three species of rust-fungi are known to affect the leaves of 
various willows in the United States. One of these is very 

341 



342 



MANUAL OF TREE DISEASES 



common and is found generally distributed throughout the 
northern states. The other two are apparently rare and 

are known only 
in Colorado and 
Utah. The leaf- 
rusts are impor- 
tant on young trees 
because defoliation 
often results. 

Symptoms. 

The three rust- 
diseases are very 
similar in appear- 
ance. In early sum- 
mer the affected 
leaves show yellow- 
ish areas on which 
are borne small 
orange-yellow pus- 
tules. These pus- 
tules appear pow- 
dery, due to the 
mass of spores they 
contain. Later in 

Fig. 70. -Powdery mildew on willow leaves. ^^le seaSOU on the 

same areas, small dark brown raised spots are formed. The 
heavily infected leaves may drop from the tree. 

Cause. 

The common willow rust is caused by Melampsora Bigeloicii 
Thiim. This fungus also causes a rust of the leaves of larch 
(see page 212). The spores (seciospores) borne in the pus- 
tules on the larch leaves infect the willow leaves. The orange- 




WILLOW DISEASES 343 

yellow pustules contain urediniospores which infect other willow 
leaves. In this way the fungus spreads from willow to willow 
during the summer. In the autumn teliospores are formed 
under the epidermis in dark brown spots. These over-winter 
and produce basidiospores which infect the larch needles in 
early spring. Two other closely related species, Melampsora 
confiuens (Persoon) Cast, and M. alpina Juel, occur on willows 
in Colorado and Utah. The former species has its aecial stage 
on currants and gooseberries (Ribes) and the latter on species 
of Saxifraga. 

Tar Leaf-Spot 

Caused by Rhytisma salicinum Fries 

Willow leaves are occasionally seen having thick tar-like spots 
on them. The spots are usually about a quarter of an inch 
across. The causal fungus is a close relative of that causing the 
tar leaf-spot of maple. The discussion of the life history and 
control of the maple fungus on page 223 applies in all respects 
to this willow leaf-spot. 

Common White Wood-Rot 

Caused by Fomes igniarius Fries 

Willows, among many other kinds of deciduous trees such as 
poplar, beech, oak and maple, are attacked by the false-tinder 
fungus. The wood is reduced to a white or yellowish punk 
marked with numerous concentric narrow black lines. Enor- 
mous losses in timber values are caused by this rot in the forest, 
where it is much more common than in open stands or individual 
ornamental trees. The symptoms and the sporophores are simi- 
lar for all the kinds of trees affected and are described 
under poplar diseases, page 305. The hoof-shaped type of 
sporophore seems to be more common on willow than the 
shelf-like form. 



344 MANUAL OF TREE DISEASES 

White Wood-Rot 

Caused by Trametes suaveolens Fries 

Willows in eastern and central United States are commonly 
affected by this white wood-rot. The disease seems to be most 
destructive when willows are badly wounded by the breaking 
of branches or by injudicious pruning. The actual importance 
and symptoms of this wood-rot have apparently not been studied 
as but little has been published on the disease. The sporophores 
of the causal fungus are easily recognized. They are sessile, 
annual, shelf-like bodies, usually four or five inches broad, and 
project three or four inches from the trunk. The upper sur- 
face is convex, smooth, whitish or gray and velvety to the touch. 
The under surface is flat, white or grayish and has a chamois-skin 
texture. The pores on the under surface are large. This fungus 
occurs only on willow and produces fruiting-bodies abundantly. 
For a general discussion of the life history and control of wood- 
rot fungi in living trees, see page 64. 



CHAPTER XXXIII 
TREE SURGERY 

Many of the diseases and injuries of the bark and wood of 
valuable shade and ornamental trees may be controlled by re- 
moving the affected parts. Two factors determine whether 
surgical methods are advisable; the value of the tree should 
justify the expense and the men who do the work should be 
capable. As to the expense that is justified, the owner alone 
can judge after estimating the cost of the work. The capabil- 
ities of the workmen largely determine whether or not the ex- 
pense involved will be wasted. The surgical work done by many 
individuals and companies is both worthless and injurious to 
the tree. For this reason the public has become skeptical re- 
garding the value of tree surgery. There is nothing mysterious 
nor difficult about the practice and it can be done by any one 
who understands the structure and physiology of trees and the 
general nature of the diseased conditions of wood and bark. 
Ability to work in all parts of the tree and handle the necessary 
tools greatly facilitate the operations. The following discussion 
is written primarily as a guide in surgical methods. At the same 
time it will aid the reader in critically examining work done by 
others. 

The heartwood of the tree may be removed without in any 
way interfering with its life processes. The removal of a large 
area of heartwood may, however, weaken the tree and some 
bracing or bolting may be necessary. The sapwood and bark 
must be carefully conserved. This is easily appreciated when 
one considers that these tissues are the communicative channels 

345 



346 MANUAL OF TREE DISEASES 

for the upward movement of water and raw food materials from 
the roots to the leaves and for the downward movement of the 
manufactured foods from the leaves to all parts of the twigs, 
branches, trunk and roots. If the bark and sapwood are injured 
at any place to the extent that the tree is partially girdled, the 
water and food materials pass with difficulty around the injured 
area. Under some conditions, the limbs and roots directly 
above and below the injury will suffer and may die. It is, there- 
fore, necessary in all tree surgery work to conserve as much of 
the living bark and sapwood as possible. Whenever these tis- 
sues are exposed in the process, they must be immediately pro- 
tected by a coating of shellac or they will soon dry out to such 
an extent that the living cells will die. This precaution is es- 
pecially necessary to protect the delicate cambium tissue which 
lies between the bark and sapwood and is the formative region in 
which these tissues are being constantly generated. 

Two results are accomplished by surgical methods ; first, the 
unsightly diseased parts of the tree are removed ; and secondly, 
the enlargement of the diseased area is prevented, and in the 
case of diseases caused by living organisms, the source of further 
infection is removed. Tree surgery may be divided into two 
distinct types : by pruning, the affected limbs or roots are cut 
off; and by lesion excision, only the affected area of bark or 
wood is removed. 

Pruning 

There are certain fundamental principles which must be ob- 
served, if pruning is to be a successful eradication measure. The 
work of pruning should begin at the top of the tree and the 
greatest care must be taken to avoid injury to the bark during 
the operation. Rubber-soled shoes should be worn by the 
workmen. Iron-climbers, such as are worn to climb poles, 
should never be used in trees. Ladders are the most effective 
and least injurious means of reaching all parts of the tree. The 



TREE SURGERY 347 

workman should carry a saw, a bucket of wound dressing and 
a large brush. When diseased twigs are to be removed, pruning 
shears should be used. In sawing off limbs of any size, care 
must be taken to prevent splitting and tearing of the bark below 
the cut. Two preliminary cuts should be made about a foot 
from the base of the limb ; a shallow cut from below and then 
the limb is sawed off beyond the lower cut. The final cut is 
then made by sawing even with and parallel to the trunk or 
limb from which the stub projects. It is even advisable to 
make a preliminary cut at the base of the stub, to guard further 
against peeling the bark. The shoulder of the stub should be 
removed, even though it results in a larger wound. A cut made 
to conform with the outline of the parent branch or trunk will 
heal much more rapidly than if a stub, even less than an inch, 
is left. In the case of large pruning wounds, a sharp chisel and 
mallet are necessary to smooth oft' the cut surface, especially in 
shaping the edge of the bark and making the cut as close to the 
body as possible all around the wound. A sharp knife is then 
useful for the final smoothing of the bark, and as this proceeds a 
coating of good shellac should be applied with a brush. Unless 
this is done, following the knife closely, the bark will dry out 
and the cambium will be killed back and thus delay the healing 
process. The wound, if large, should be pointed above and be- 
low, since round wounds do not heal rapidly on the upper and 
lower sides. The bark often dies at these places and two new 
unprotected injuries result which will need further attention. 

For small wounds of an inch or less, where the cut surface 
does not bleed excessively, two operations are sufficient ; first saw 
off the limb and then apply a good dressing, — coal-tar or as- 
phaltum. For this purpose the pruner carries a small can of the 
wound dressing and applies it with a brush. For all larger 
wounds several steps are necessary, especially when the wound is 
more than two or three inches in diameter. The following 
operations are required in order to leave the wound in such a 



348 MANUAL OF TREE DISEASES 

condition that it will not afford entrance to decay-producing 
organisms. If the wound bleeds profusely, it may be necessary 
to wait a few days until the surface dries, otherwise the opera- 
tions described below should follow in a day or so, or better 
immediately. 

Disinfecting Wounds 

The woody portion of the cut should be disinfected. Three 
methods may be used : 

1 . Swabbing the wound with a water solution of a disinfectant. 
Mercuric chloride or copper sulfate are advised. Mercuric 
chloride may be bought in tablet form. One or two tablets to 
a quart of water is sufficient. If copper sulfate is used, a solu- 
tion should be made by dissolving one ounce of copper sulfate 
in three quarts of water. 

2. The surface of the wound may be seared with a gasoline 
torch. This method should be employed especially when the 
wound continues to bleed. 

3. The wound may be painted with a wood preservative, 
ordinary creosote being satisfactory. It penetrates into the 
wood much further than a water solution of an antiseptic sub- 
stance. It should not be used, however, on bark. 

Wound Dressings 

The next important operation is the application of a durable 
wound dressing. Two difficulties must be overcome in applying 
this : first, the wound is usually moist and it is difficult to make 
some dressings adhere tenaciously ; and second, the surface will 
check on drying and no dressing will prevent this. These diffi- 
culties may be somewhat overcome by applying a temporary 
dressing followed, after the surface begins to check, by the per- 
manent dressing. 

Tar, asphaltum, lead paint, slater's cement and many "tree 
paints" are available as wound dressings. Ordinary coal-tar 



TREE SURGERY 349 

is most generally used and is recommended. Asphaltum, both 
melted and dissolved, is also a desirable substance to use. 

Crude tars are obtained largely from bituminous coal, pe- 
troleum and wood, when these substances are burned in closed 
retorts. The temperature at which the distillation is carried 
out determines largely the chemical character of the crude tar. 
The products are named according to their source, coal-tar, 
oil-tar and wood-tar. The larger part of the coal-tar is produced 
in coke- and coal-gas manufactories. Bituminous coal is dis- 
tilled at temperatures varying from 1500° to 3000° Fahr. until 
the charge has been reduced to coke. The tar, resulting as a 
by-product, varies in its nature according to the character of 
the coal and the temperature used. The tar contains mainly 
hydrocarbons of the aromatic series, such as phenols, naphtha- 
lenes and anthracenes. Coal distilled at relatively lower tem- 
peratures contains less of the aromatic hydrocarbons and a 
greater or less quantity of paraffin hydrocarbons. Oil-tar is 
largely produced as a by-product of water-gas production. This 
tar is characterized by an absence of the phenols (tar-acids) and 
a greater or less quantity of the different hydrocarbons. Wood- 
tars are quite different and contain, in particular, less of the 
aromatic hydrocarbons. Thus it is seen that crude tars may 
vary greatly and while some make suitable wound dressings 
because of their consistency and chemical nature, others do not. 

In the further distillation of crude tars, three general classes 
of substances are obtained, — oils lighter than water, oils heavier 
than water and pitch or refined tar. The oils heavier than water 
are known as creosotes. Carbolineum is a trade name for a 
coal-tar creosote distilled at a high temperature. Creosote or 
carbolineum are not recommended for wound dressings, since 
neither is of a satisfactory consistency for making a permanent 
coating. In addition, they penetrate deeply and are said to 
injure, in many cases, the living tissues around the wound. The 
crude tars (usually coal-tar) are most generally used and are 



350 MANUAL OF TREE DISEASES 

the best all-round dressings. It should be remembered that 
coal-tar contains a large percentage of the more toxic substances 
(phenols, and the like) than does oil-tar, which contains no 
phenols. The refined tars (pitch) are in all cases less toxic and 
less fluid. The tars must be chosen with regard to their physi- 
cal as well as chemical properties, since they must be durable 
in hot, as well as in cold weather. 

Another pitch-like compound, asphaltum, is highly recom- 
mended. This is the residuum of the distillation of western 
petroleum. Its toxicity has been little investigated but it ap- 
pears to be a desirable wound dressing. It is durable and the 
distillations running to high temperatures (200°— 285° Fahr.) 
leaves an asphaltum which remains solid at the temperatures 
to which it will be exposed as a wound dressing. It must be 
applied heated to the melted condition, or dissolved in ben- 
zene or other liquid petroleum products (varnolene is recom- 
mended). Many "tree paints" are solutions of asphaltum. 
The solvent used in some of these paints often kills the living 
tissues around the wound. Pure white lead paint makes a 
good dressing which prevents checking to some extent. It 
must be renewed frequently. 

Slater's cement, although not much used, is said to make a 
suitable dressing. The wound should first be painted with a 
disinfectant since this cement has no fungicidal properties. The 
cement remains plastic and does not crack. Before recommend- 
ing, it should be determined whether or not it actually prevents 
infection. 

The capping of pruning wounds and the covering of exposed 
surfaces with sheet metal is sometimes advised. There are 
many reasons why such a practice is unscientific. In nailing 
on the sheet metal, many small cracks are made in the wood. 
Those which extend back under the cover cannot be reached by 
a fresh coat of any dressing. The cap cannot form a permanent 
or absolute covering and moisture will in time accumulate be- 



TREE SURGERY 351 

neath it ; this results in ideal conditions for infection by wood- 
rotting fungi. 

Reinforced dressings may be used which seem to supply the 
theoretical advantages sought by capping and yet are not sub- 
ject to the disadvantages of sheet metals. The wound is first 
given a thorough coat of the dressing and this is left to dry for 
a day or two. Then cotton padding an eighth of an inch in 
thickness is soaked in the dressing and pressed against the wound. 
It is then trimmed with a sharp knife so as to extend out to the 
bark and not beyond it. If the padding extended over the bark, 
it w^ould be pushed off during the process of callus formation. 
Finally, after a few days, another coat of the dressing is ap- 
plied. Tar for the first application and asphaltum for the 
latter two are recommended. 

Little need be said concerning the method of applying the 
liquid or semi-liquid dressings. They may be applied with a 
brush or swab. Dressings which need to be heated, to make 
them fluid, require a contrivance for this purpose. A tinner's 
outfit is probably as adaptable as anything. More than one 
coat of most dressings is desirable and frequent inspections 
should be made to determine the need of renewing it. 

Lesion Excision 

The removal of diseased or injured tissues may be accom- 
plished without cutting away the entire affected organ as is 
done in pruning. Lesion excision is limited to the eradication 
of diseased bark and wood of the trunk and larger branches. 
When the cause of the diseased condition is a parasite, it is re- 
moved along with the affected tissue. Cankers and wood-rots 
are the two common types of diseases which are controlled by 
lesion excision. 

Cankers consist, in general, of dead areas of bark. They are 
more or less definite in outline. In removing the diseased tissue, 



352 MANUAL OF TREE DISEASES 

caie must be taken to cut back into the healthy bark beyond 
the advance of any parasite which may be present. The bark 
should be cut at right angles to the surface and the edges should 
be clean and smooth. The wood beneath the cankered area 
should in most cases be removed to the depth of a half inch or 
more. Then the ends of the wound must be shaped to a point. 
All of this work can be done with a draw-shave, chisel, gouge, 
mallet and heavy sharp knife. The diseased tissue which is 
removed should be burned, since it may serve as a source of 
infectious material. The Endothia canker of chestnut (see 
page 140) affords a good example of the care necessary to remove 
all affected tissues. The early failures to prevent the extension 
of the cankers by incision of the bark only was later explained 
by the discovery that the mycelium penetrated into the wood, 
even to the fifth annual ring at times. With this fact in mind, 
successful treatment of the cankers is effected by the removal 
of all diseased wood beneath the cankered area. The tendency 
of certain parasites to spread up and down the limb or trunk in 
the cambium region or sapwood, without causing apparent in- 
jury to the overlying bark, presents another difficulty in canker 
excision. This habit of growth is common for many parasitic 
fungi and bacteria. The mycelium of a fungus may spread in 
this way for many inches above and below the cankered area. 
Its presence is usually evident as dark colored streaks in the 
sapwood. 

When the lesions extend deeply and extensively into the wood 
as in the case of heartwood- and sapwood-rots, the complete 
removal of all the affected tissue is very difficult. Large cavi- 
ties must be excavated, which is a tedious and an expensive 
operation. Tissues in the advanced stages of decay are easily 
detected and removed. Such wood is usually soft and crumbly. 
But if the excavating stops with the removal of the punky wood 
only, no benefit will result from the work, for many of the fungi 
which cause wood-rots advance a considerable distance into the 



TREE SURGERY 353 

wood beyond the limits of evident decay and discoloration. A 
layer of apparently healthy wood outside the discolored area 
must be removed from all sides of the cavity to make sure that 
all of the mycelium is eradicated. 

The size of the opening of the cavity should be no greater than 
is absolutely necessary, as healthy sapwood and bark must be 
conserved. The form of the opening will depend on conditions, 
except that it must be pointed below and above, as in the case 
of canker excision, to insure rapid healing at these places. The 
edges of the cavity must be clean cut and should be shaped with 
a chisel or gouge. The bark may be finally shaped with a strong 
knife. Shellac should be applied to the bark and sapwood as 
this is done. 

For cavity work, gouges of various sizes, chisels, a mallet and 
a heavy knife are needed. In opening a diseased area, it is 
often necessary to cut away healthy sapwood and bark in order 
to get at the decayed wood with the gouge. Often the diseased 
wood must be followed for some distance above and below the 
original opening. Instead of making other small holes in the 
bark and sapwood, a narrow continuous opening is much better. 
The bridges of healthy bark and sapwood left, when holes are 
made, are bad practice for two reasons : the decayed wood is 
not as effectively removed and the bridges are likely to die and 
may be the source of future difficulty. 

Cavity Treatments 

At this point it must be decided whether or not the cavity is 
to be filled. Cavities may be treated in one of three ways : 
(1) left open; (2) closed by sheet metal conforming to the 
position of the original bark ; and (3) filled with solid sub- 
stances. The last method is the most commonly practiced and 
is the most expensive and, in the main, least scientific. 

If the cavity is not to be filled, no further shaping is neces- 
2a 



354 MANUAL OF TREE DISEASES 

sary except that it should be left so that it will not hold water. 
The bottom should slope outward at a sharp angle from all 
directions. After the removal of all the diseased wood, the 
surface of the cavity should be covered with a good wound 
dressing (see page 348). In the case of cavities in which a 
large amount of heartwood is exposed, the wood can very ad- 
vantageously be painted with creosote or carbolineum. This 
will serve excellently as a penetrating and permanent disinfect- 
ant. Then one or more coats of a dressing such as asphaltum 
(heated to liquid condition) or coal-tar should be applied. After 
such treatment the work is finished so far as remedying the dis- 
eased condition is concerned. The diseased part of the tree has 
been eradicated and the wounded surface protected. There are 
several additional steps often taken which are non-essential and 
even harmful to the success of the work. In other words, cavi- 
ties are better left open. The orchardist, especially, should 
never spend money filling cavities or even tinning them. If 
the cavity is left open, it can be inspected yearly and any neces- 
sary renewals of the dressings made. The only advantage 
claimed for tinning cavities is that the holes are closed up, the 
tree appears normal in shape and the metal furnishes a support 
for the developing callus. In the case of narrow slit-like cavities, 
this may eventually result in complete healing over. 

Tinning is not to be advised on large cavities. It is mainly 
advantageous for those which may be expected to heal ulti- 
mately. The main benefit derived from the tinning is the sup- 
port of the callus which would otherwise roll inside the cavity. 
The disadvantage of tinning is mainly that the surface of the 
cavity is no longer visible. The opening of the cavity must be 
so shaped that the metal will lie without wrinkling. Also a 
band of bark, about one-half to three-quarters of an inch wide, 
must be removed so that the metal may be seated on the wood 
and nailed fast. The metal should be placed even a little below 
the inner surface of the bark. Zinc and copper are the best 



TREE SURGERY 355 

sheet metals to use. Galvanized iron, tin plated sheet-iron and 
uncoated sheet-iron may be used if kept painted. The tensions 
developed when a tree twists and bends under wind pressure 
must be taken into account in fitting the sheet metal. 

Two things are attempted in filling cavities : (1) to prevent 
the entrance of fungi and insects ; and (2) to strengthen the tree. 
As a matter of fact they accomplish neither and there is no sound 
argument in most cases for the additional cost which filling en- 
tails. If the cavity is to be filled, it must be cut back on all sides 
so that the cavity enlarges abruptly just inside the opening. A 
shell of about two inches should be left if possible as a shoulder 
to hold in the filling. If the opening is so wide that a shoulder 
cannot be shaped to hold the filling, reinforcing of some kind 
should be used. If the shell is thin or the cavity is a long one, 
over two or three feet, it should be bolted. Bolts should be used 
at intervals of two feet. The manner of placing and size of bolt 
will depend on circumstances. After the holes are bored, areas 
of bark are cleaned away so that the washers and nuts can be 
countersunk. The holes should then be tarred and the bolts 
fastened in place after which tar should be applied again. If 
the shell is thick, nails may be driven into the wood to serve as 
reinforcing to hold the filling. Also wires fastened to the nails 
and bolts may be used. If the cavity is very large, ordinary 
reinforcing steel rods wired to the bolts may be utilized. 

The two types of fillings generally used are concrete and 
asphaltum. Concrete may be put in dry or wet. Dry con- 
crete is built up by tamping and troweling. i\.ccount must be 
taken of the size of the tree and amount of swaying in the wind, 
and joints used or the concrete will crack and fall out. Joints 
should slope downward and drain easily. Newspaper or heavy 
tarred paper and felt are used to separate the blocks. Bricks 
and stones may be tamped in where large fillings are made. If 
wet concrete is used, a facing of canvas and oilcloth is employed 
over the opening to shape the surface. In all cases the surface 



356 MANUAL OF TREE DISEASES 

of the concrete must project no further than the sapwood. The 
calhis will then roll over the edge and be supported by the con- 
crete. The outer surface should be left rough and tar or cement 
paint used to waterproof the surface of the filling. 

When asphaltum is employed, it is generally mixed with sand, 
sawdust or excelsior. A system of briquettes made of asphalt 
and sawdust is often used to build up a wall, making the face of 
the filling. This is laid up as a brick wall is made, each briquette 
being first dipped in hot asphalt. The briquettes next the edges 
of the cavity are nailed to the wood. Reinforcing may be 
adopted as in concrete fillings, and the space behind the bri- 
quette wall is filled with asphalt mixed with sawdust or sand. 
Sheet metal may be used instead of the briquettes but it is liable 
to tear loose with the bending of the tree. 

In all tree surgery work, the ingenuity of the worker is called on 
to figure out what is best under the existing circumstances. The 
book, "Practical Tree Repair" by Peets, and an article in the 
1913 Yearbook of the Department of Agriculture by Collins, give 
many details of this kind of work which are not included here. 

The fact to be kept in mind, however, is that most tree sur- 
gery becomes necessary only because small injuries were not 
cared for. Proper pruning, wound dressings, bracing, bolting, 
chaining, guying and all such operations are necessary to pre- 
vent injuries. If such points are given attention, very little sur- 
gical work need be done. 

References 

Collins, J. F. Practical tree surgery. U. S. Dept. Agr. Yearbook 

1913 : 163-190, pis. 16-22. 1914. 
Peets, Elbert. Practical tree repair, pp. 1-265. (Illustrated.) 1913. 
Selby, A. D. Dressings for pruning wounds of trees. Ohio Agr. 

Exp. Sta. Circ. 126 : 163-170. 1912. 
Selby, A. D. Tree fillings and wound dressings for orchard and 

shade trees. Ohio Agr. Exp. Sta. Circ. 150 : 61-63. 1915. 
Gaskill, Alfred. The planting and care of shade trees. Forest Park 

Reservation Commission of New Jersey, pp. 1-128, pis. 1-5, 

figs. 1-43. 1912. 



CHAPTER XXXIV 
SPRAYING AND DUSTING FOR LEAF DISEASES 

In the absence of experimental data on the spraying or dusting 
of shade and ornamental trees for the control of leaf diseases, 
only very general recommendations can be made. The various 
leaf-spots, powdery mildews and sooty molds that often affect 
trees doubtless can be controlled by fungicides applied to the 
leaves. General directions will be found under the discussion 
on the powdery mildews for the control of these fungi (see 
page 37). These recommendations are based largely on the 
results obtained in controlling powdery mildews on fruits and 
small ornamentals. In order to control the many leaf-spot 
diseases, data should be available on the life history of the patho- 
genes (so that the time of applications might be determined), 
the strength and type of fungicide to use and the number of 
applications that are necessary. Without a definite knowledge 
of these facts, spraying can only be advised as an experimental 
practice. 

The source of primary infection in the spring for most leaf- 
spot diseases is in the old dead leaves on the ground. These 
should be raked together and burned in the late autumn. Some 
of the leaf-spot fungi also attack the twigs and when this is the 
case the diseased twigs should be pruned off. Unless these 
eradication measures are taken, spraying will be less successful 
in controlling the disease. 

The three common fungicides are bordeaux mixture, lime- 
sulfur solution and sulfur dust. The toxic agent in the first is 
copper and in the latter two, sulfur. These substances are ap- 

357 



358 MANUAL OF TREE DISEASES 

plied, to the foliage in a finely divided form in order to cover the 
leaves as completely as possible. Then when the fungous spores 
lodge on the leaf, they are either killed outright or soon after 
germination by contact with the copper or sulfur. Thus it is 
seen that the use of spray and dust mixtures will prevent leaf- 
spot diseases only when the mixture is applied before infection 
has taken place. In addition it should be remembered that 
while the leaves are growing, the increase in leaf surface exposes 
unprotected tissue and therefore applications must be renewed 
frequently. Applications should be made before rain periods, 
since the spores are disseminated and produce infection while 
the leaves are wet. The fungicides will not wash off materially. 
After a time they weather and are no longer efficient. In gen- 
eral, applications should be made at intervals of ten or fourteen 
days. 

So far as is known, bordeaux mixture, lime-sulfur or sulfur 
dust may be used at the ordinary concentrations without injury 
to trees. The first two are liquid mixtures and the latter is 
applied dry. For large trees the spraying machines for liquid 
fungicides must develop a high pressure. Such machines are 
expensive. Blowers to apply sulfur dust are less expensive. 
Lime-sulfur is obtained on the market in concentrated form. It 
usually may be used with safety at a dilution of one part of 
the concentrate to fifty parts of water. Dry sulfur for dusting 
must be finely ground. Ten parts of dry arsenate of lead to 
ninety parts of sulfur-flour is recommended. The arsenate of 
lead makes the distribution of the sulfur more uniform and 
gives it greater adhesive qualities. Bordeaux mixture in various 
forms and strengths may be bought ready for diluting. Home- 
made bordeaux mixture, however, is more efficient and is not 
difficult to prepare. It is generally used at the strength 
designated as 5-5-50, that is, 5 pounds of quick-lime, 5 pounds 
of copper sulfate and 50 gallons of water. 

Bordeaux mixture is made as follows : Prepare a stock solu- 



SPRAYING AND DUSTING FOR LEAF DISEASES 359 

tion of copper sulfate by hanging the crystals in a cloth bag in a 
barrel of water. As many pounds of copper sulfate should be 
placed in the bag as there are gallons of water in the barrel. 
After several hours the copper sulfate will have dissolved. 
Next prepare a stock solution of lime which will contain one 
pound of quick-lime in each gallon of water. The proper 
amount of stone-lime is slaked, enough water being added to 
prevent the lime from burning. When all the lime is powdered, 
enough water is added to make the strength one pound of lime 
to one gallon of water. To make fifty gallons of bordeaux mix- 
ture, take five gallons of the stock solution of copper sulfate 
and pour it into the spray tank. Add about thirty gallons of 
water and then pour in five gallons of the stock solution of 
lime and stir the mixture thoroughly. Enough water is then 
added to make fifty gallons in all. 



APPENDIX 



Common Names of Trees 



A LIST of the common names of trees used in this manual 
is given below with the scientific name opposite each. In 
most cases, the common name recommended by Sudworth ^ is 
adopted. 



Alder (general) 
Alpine fir 
Alpine larch 
Arbor-vitsB (general) 
Arbor-vitsB (specific) 
Ash (general) 
Aspen 

Bald cypress 
Balm of Gilead 
Balsam fir 
Basswood (general) 
Basswood (specific) 
Beech 

Birch (general) 
Black ash 
Black gum 
Black jack oak 
Black poplar 
Black spruce 
Black walnut 
Box-elder 
Buckeye (general) 
Bur oak 
Butternut 
California buckeye 
Carolina hemlock 



Alnus sp. 

Abies lasiocarpa Nutt. 

Larix Lyallii Pari. 

Thuja sp. 

Thuja occidentalis Linn. 

Fraxinus sp. 

Populus tremuloides Michx. 

Taxodium distichum Rich. 

Populus balsamifera Linn. 

Abies balsamea Mill. 

Tilia sp. 

Tilia americana Linn. 

Fagus grandifolia Ehrh. 

Betula sp. 

Fraxinus nigra Marsh. 

Nyssa sylvatica Marsh. 

Quercus marilandica Muench. 

Populus nigra Linn. 

Picea mariana B. S. P. 

Juglans nigra Linn. 

Acer Negundo Linn. 

Msculus sp. 

Quercus macrocarpa Michx. 

Juglans cinerea Linn. 

j^sculus californica Nutt. 

Tsuga caroliniana Engelm. 



* Sudworth, G. B. Check list of the forest trees of the United States, their 
names and ranges. U. S. Dept. Agr. Div. Forestry Bui. 17 : 1-144. 1898. 

361 



362 



APPENDIX 



Catalpa (general) 
Cedar (general) 

Chestnut 
Chestnut oak 
Chinquapin 
Colorado blue spruce 
Cottonwood 
Coulter pine 
Cuban pine 
Dogwood 
Douglas fir 
Dwarf juniper 
Eastern hemlock 
Eastern larch 
Elm (general) 
Engelmann spruce 
European chestnut 
Fir (general) 
Eraser fir 
Grand fir 
Gray pine 
Green ash 

Hackberry (general) 
Hardy catalpa 
Haw (general) 
Hemlock (general) 
Hickory (general) 
Horse-chestnut 
Incense cedar 
Jack pine 
Japanese chestnut 
Jeffrey pine 
Juniper (general) 
Knob-cone pine 
Larch (general) 
Large-tooth aspen 
Limber pine 
Loblolly pine 
Locust (general) 
Locust (specific) 
Lodge-pole pine 
Lombardy poplar 
Long-leaf pine 
Maple (general) 



Catalpa sp. 

ChamcBcyparis sp. and Libocedrus 

sp. 
Castanea dentata Borkh. 
Quercus Prinus Linn. 
Castanea pumila Linn. 
Picea Parryana Parry 
Populus deltoides Marsh. 
Pinus Coulteri Lamb 
Pinus heterophylla Sudw. 
Cornus florida Linn. 
Pseudolsuga taxifolia Brit. 
Juniperus communis Linn. 
Tsuga canadensis Carr. 
Larix laricina (Du Roi) Koch. 
Ulmus sp. 

Picea Engelmanni Engelm. 
Castanea saliva Mill. 
Abies sp. and Pseudolsuga sp. 
Abies Fraseri Poir. 
Abies grandis Lindl. 
Pinus Sabiniana Dougl. 
Fraxinus lanceolala Borkh. 
Celtis sp. 

Catalpa speciosa Warder 
Cratcegus sp. 
Tsuga sp. 

Carya or Hicoria sp. 
/Esculus Hippocaslanum Linn. 
Libocedrus decurrens Torr. 
Pinus Banksiana Lamb. 
Castanea crenala Sieb. and Zucc. 
Pinus Jeffreyi 
Juniperus sp. 
Pinus attenuala Lemmon 
Larix sp. 

Populus grandidentata Michx. 
Pinus flexilis James 
Pinus Toeda Linn. 
Robinia sp. 

Robinia Pseudacacia Linn. 
Pinus conlorla Loud. 
Populus nigra ilalica Du Roi 
Pinus palustris Mill. 
Acer sp. 



APPENDIX 



363 



Monterey pine 

Mountain ash (general) 

Mountain juniper 

Noble fir 

Norway pine 

Norway spruce 

Nut pine 

Oak (general) 

Ohio buckeye 

One-seed juniper 

Paper birch 

Pine (general) 

Pitch pine 

Pond pine 

Poplar (general) 

Red ash 

Red juniper 

Red maple 

Red oak 

Red spruce 

River birch 

Rocky Mountain juniper 

Sand pine 

Scarlet oak 

Scotch pine 

Scrub pine 

Service-berry (general) 

Shasta red fir 

Short-leaf pine 

Silver maple 

Single-leaf pine 

Sitka spruce 

Spruce (general) 

Spruce pine 

Striped maple 

Sugar pine 

Swiss stone pine 

Sycamore 

Table-mountain pine 

Utah juniper 

Western chinquapin 

Western hemlock 

Western larch 

Western white pine 

Western yellow pine 



Pinus radiata Don. 

Sorbus sp. 

Juniperus sabinoides Sarg. 

Abies nobilis Lindl. 

Pinus resinosa Ait. 

Picea excelsa Link 

Pinus edulis Engelm. 

Quercus sp. 

Msculus glabra Willd. 

Juniperus monosperma Sarg. 

Betula papyrifera Marsh. 

Pinus sp. 

Pinus rigida Mill 

Pinus serotina Michx. 

Populus sp. 

Fraxinus pennsylvanica Marsh. 

Juniperus virginiana Linn. 

Acer rubrum Linn. 

Quercus rubra Linn. 

Picea rubra Dietr. 

Betula nigra Linn. 

Juniperus scopulorum Sargent 

Pinus clausa Sarg. 

Quercus coccinea Mueneh. 

Pinus sylvestris Linn. 

Pinus virginiana Mill. 

Amelanchier sp. 

Abies magnifica Murr. 

Pinus echinata Mill. 

Acer saccharinurn Linn. 

Pinus rnonophylla Torr. and Frem. 

Picea sitchensis T. and M. 

Picea sp. 

Pinus glabra Walt. 

Acer pennsylvanicum Linn. 

Pinus Lambertiana Dougl. 

Pinus Cembra Linn. 

Platanus occidentalis Linn. 

Pinus pungens Lamb. 

Juniperus utahensis Lemm. 

Castanopsis chrysophylla de C. 

Tsuga heterophylla Sarg. 

Larix occidentalis Nutt. 

Pinus monticola Dougl. 

Pinus ponderosa Laws. 



364 



AP'PENDIK 



White ash 
White birch 
White cedar 
White elm 
White fir 
White oak 
White pine 
White spruce 
Yellow birch 
Yellow buckeye 
Yellow cedar 
Yellow oak 
Yellow poplar 



Fraxinus americana Linn. 
Betula populifolia Marsh. 
Chamoecyparis thyoides B. S. P. 
Ulmus americana Linn. 
Abies concolor Parry 
Quercus alba Linn. 
Pinus Strobus Linn. 
Picea canadensis B. S. P. 
Betula lutea Michx. f. 
/Esculus octandra Marsh. 
Chamcecyparis nootkatensis Spach. 
Quercus velutina Lam. 
Liriodendron Tulipifera Linn, 



Synonymy of Polypore Names 

Following is a list of the polypore names used in this 
manual. Opposite each is the name applied to the same 
fungus by Murrill ^ in the North American Flora. 



Fames annosus Fries 
Fames applanatus Fries 
Fames Earlei (Murr.) Sace. 
Fames Everharlii (Elhs and Gall.) 

Schrenk 
Fames fomentarius Fries 
Fames fraxinaphilus Peck 
Fames fulvus Fries 

Fom,es geotropus Cooke 
Fames igniarius Fries 

Fames juniperinus Schrenk 

Fames officinalis Fries 
Fames pinicola Fries 
Fames rimosus Berkeley 
Fames raseus Fries 

Fames texanus (Murr.) Hedg. and 

Long 
Polyparus amarus Hedgcock 



Fames annosus (Fries) Cooke 
Elfvingia megalama (Lev.) Miur. 
Pyrapolyparus Earlei Murr. 
Pyrapolyparus Everharlii (Ell. and 

Gall.) Murr. 
Elfvingia fomentaria (L.) Murr. 
Fames fraxinaphilus (Peck) Sacc. 
Pyropolyporus fulvus (Scop.) 

Murr. 

Pyropolyporus igniarius (L.) 

Murr. 
Pyropolyporus juniperinus 

(Schrenk) Murr. 
Fames laricis (Jacq.) Murr. 
Fames ungulatus (Schaeff.) Sacc. 
Pyropolyporus Robinice Murr. 
Fames raseus (Alb. and Schw.) 

Cooke 
Pyropolyporus texanus Murr. 



' Murrill, W. A., North American Flora, 9 : 1-131. 1907. 



APPENDIX 



365 



Pohjporus Berkeleyi Fries 
Polyporus borealis Fries 
Polyporus betulinus Fries 
Poly poms croceus Fries 

Polyporus dryadeus Fries 
Polyporus Ellisianus (Murr.) Long 
Polyporus frondosus Fries 

Polyporus ohtusus Berkeley 

Polyporus Rheades Fries 
Polyporus Schweinitzii Fries 

Polyporus sqtiamosus Fries 

Polyporus sidphureus Fries 

Trametes pint Fries 
Trametes suaveolens Fries 



Grifola Berkeleyi (Fries) Murr. 
Spongipellis borealis (Fries) Pat. 
Piptoporus suberosus (L.) Murr. 
Aurantiporus Pilotce (Schw.) 

Murr. 
lonotus dryadeus (Fr.) Murr. 
Tryomyces Ellisianus Murr. 
Grifola frondosa (Dicks.) S. F. 

Gray 
Spongipellis unicolor (Schw.) 

Murr. 
lonotus dryophilus (Berk.) Murr. 
PhoEolus sistotremoides (Alb. and 

Schw.) Murr. 
Polyporus caudicinus (Scop.) 

Murr. 
Lailiporus speciosus (Batarr.) 

Murr. 
Porodo'dalia pini (Thore) Murr. 
Trametes suaveolens Fries 



Glossary 

Acervulus (aeervuli). Open, saucer-shaped, asexual fruiting-body. 
.^ciospore. One of the types of spores formed by the rust-fungi. 

.iEciospores are produced in the blisters on conifers in the ease 

of the blister-rusts. The juniper and cedar rust-fungi form 

aeciospores on the pomaceous host. 
Ascospore. Sexually formed spores which are borne within a sac 

called an ascus. The asci are in turn borne on or in various 

tj^pes of fruiting-bodies. 
Ascus (asci). Sac-like structures containing ascospores. Asci are 

borne in open or closed fruiting-bodies. Perithecia contain asci. 
Bacterium (bacteria). SmaU, microscopic plants. Plants consist 

of single cells, which may be motile. Parasitic forms cause in- 
fectious diseases of plants and animals. 
Basidiospore. Short lived spores borne on germ-tubes of teliospores 

in the rust-fungi. They are forcibly discharged and are carried 

by the wind. 
Cambium. Region of growth in a woody stem or root, at which wood 

is formed on the inside and bark on the outside. 
Canker. A dead area of bark. 
Chlorophyl. The green coloring material produced in the leaves of 

the higher plants. Chlorophyl is instrumental in making starch 

from carbon dioxide gas and water. 



366 APPENDIX 

Enzyme. A complex chemical compound capable of causing the 
transformation of certain organic substances into substances of 
greater or less complexity without itself entering into the product. 

Epiphytotic. A plant disease which assumes an unusual and generally 
destructive nature in a locality. Usually called an epidemic, 
which term refers only to human diseases. 

Fruiting-body. Large or small, open or closed structures made of 
mycelium in which the spores of fungi are formed. 

Fungus. Simple plants lacking chlorophyl. Consisting of mycelium 
which may be massed to form large fruiting-bodies. Fungi 
obtain food by decomposing living or dead plant and animal tissue. 

Fusiform. Spindle-shaped. 

Germ-tube. A short tube which grows from a viable spore. The 
germ-tube then branches and a new mycelium is formed if growth- 
conditions are suitable. 

Gill. The pendent plates or lamellae found on the under side of 
toadstools. The spores of the fungus are borne on the sides of 
the gills. 

Haustorium (haustoria). Special branch of the mycelium which is 
pushed into a cell to obtain food-materials. 

Heartwood. The wood at the center of a tree, which contains no 
living cells and serves only for support. 

HetercBcious. Said of a parasitic fungus which requires more than 
one kind of host for the completion of its life history. 

Host. Any plant in which a parasite grows. 

Hypertrophy. Enlargement of a portion of a plant, as galls on limbs. 

Hypha (hyphae). Individual branches of the mycelium of a fungus. 

Infect. Said of a parasitic organism when it succeeds in establish- 
ing parasitic relations with a host-plant. 

Infection. The act of infecting, see above. 

Infection court. Any place or area of a host-plant where infection 
occurs. Also said of any place where infection is possible. 

Lesion. Any definitely diseased area in which the primary cause of 
the disease is present. 

Mycelium (myeelia). The vegetative body of a fungus, made up of 
long threads containing protoplasm. 

Parasite. An organism which lives in or on another living organism 
for the purpose of obtaining food-materials. 

Parenchymatous. Tissue composed of thin walled cells which are 
capable of further differentiation. 

Pathogene. Any factor which causes disease, usually restricted to 
living organisms which live parasitically. 

Perithecium (perithecia). A closed globose or fiask-shaped fruiting- 
body containing asci and ascospores. Spores usually forcibly 
discharged. 



APPENDIX 367 

Protoplasm. Living substance within the cells of plants and animals. 
The seat of growth and many other functions which are charac- 
teristic of living things. 

Pycnidium (pycnidia). An inclosed globose or flask-shaped fruit- 
ing-body containing simple asexual spores. 

Rhizomorph. A compact bundle of mycelium arranged parallel to 
form a root-like structure. See shoe-string root-rot, page 78. 

Saprophyte. A living organism which obtains its food-materials 
from dead organic material. See Parasite. 

Sapwood. The wood between the heartwood and bark. Sapwood 
contains living cells and is the tissue which is active in translo- 
cating food-materials to all parts of the tree. 

Sclerotium (sclerotia). A compact, more or less globose structure 
made of closely aggregated mycelium. Usually a resting body 
rich in stored food. 

Spore. A portion of the mycelium which is detached and serves as 
a propagative or reproductive body, corresponding to the seeds 
of higher plants. Spores may be formed sexually or asexually. 

Stomate. Specialized structures with an opening in the center, found 
on the surface of leaves. Stomates open and close and regulate 
the exchange of gases and water vapor between the interior of 
the leaf and the surrounding atmosphere. 

Stroma (stromata). Compact aggregation of mycelium forming a 
fungous layer. Fruiting-bodies may be formed imbedded in the 
stroma. 

Teliospore. A type of spore formed by the rust-fungi. All rust- 
fungi form teliospores and basidiospores. They may omit any 
one or all of the other stages. Teliospores in many species over- 
winter. When they germinate they form basidiospores directly. 

Urediniospore. A type of spore formed by the rust-fungi. These 
spores are produced in summer and serve to distribute the fungus 
rapidly during the growing season. Urediniospores are usually 
produced from mycelium that originated from seciospore infec- 
tion. Later teliospores are formed from the same mycelium. 

General Bibliography of Tree Diseases 

American Publications 

Atkinson, G. F. Studies of some shade tree and timber destroying 

fungi. Cornell Univ. Agr. Exp. Sta. Bui. 193 : 199-235, figs. 

56-94. 1901. 
Cook, M. T. Diseases of shade and forest trees. In The planting 

and care of shade trees. Forest Park Reservation Commission 

of New Jersey, pp. 93-124, figs. 36-43. 1912. 



368 APPENDIX 

Cook, M. T. The diseases of tropical plants, pp. 1-317, figs. 1-85. 

1913. 
Duggar, B. M. Fungous diseases of plants, pp. 1-508, figs. 1-240. 

1909. 
Freeman, E. M. Minnesota plant diseases, pp. 1-432, figs. 1-211. 

1905. 
Galloway, B. T., and Woods, A. F. Diseases of shade and ornamental 

trees. U. S. Dept. Agr. Yearbook 1896:237-254, figs. 53-57. 

1897. 
Harshberger, J. W. A text-book of mycology and plant pathology, 

pp. 1-779, figs. 1-271. 1917. 
Heald, F. D., and Wolf, F. A. A plant-disease survey in the vicinity 

of San Antonio, Texas. U. S. Dept. Agr. Bur. PI. Ind. Bui. 226 : 

1-129, pis. 1-19, figs. 1-2. 1912. 
Meinecke, E. P. Forest tree diseases common in California and 

Nevada. U. S. Dept. Agr. Forest Service, pp. 1-67, pis. 1-24. 

1914. 
Metcalf, H. Diseases of ornamental trees. U. S. Dept. Agr. Year- 
book 1907 : 483-494, pis. 58-60, fig. 52. 1908. 
Peets, Elbert. Practical tree repair, pp. 1-265. Illustrated. 1913. 
Sehrenk, Hermann von. Some diseases of New England conifers. 

U. S. Dept. Agr. Div. Veg. Phys. and Path. Bui. 25 : 1-56, pis. 1- 

15, figs. 1-3. 1900. 
Sehrenk, Hermann von. Fungous diseases of forest trees. U. S. 

Dept. Agr. Yearbook 1900: 199-210, pis. 21-25. 1901. 
Sehrenk, Hermann von, and Spaulding, P. Diseases of deciduous 

forest trees. U. S. Dept. Agr. Bur. PI. Ind. Bui. 149 : 1-85, pis. 

1-10, figs. 1-11. 1909. (Bibliography given.) 
Selby, A. D. A brief handbook of the diseases of cultivated plants 

in Ohio. Ohio Agr. Exp. Sta. Bui. 214 : 307-456, figs. 1-106. 

1910. 
Stevens, F. L., and Hall, J. G. Diseases of economic plants, pp. 1-513, 

figs. 1-214. 1913. 
Stone, G. E. Shade trees, characteristics, adaptation, diseases and 

care. Mass. Agr. Exp. Sta. Bui. 170 : 123-264, figs. 1-109. 

1916. 

European Publications 

Bourcart, E. Les maladies des plantes — leur traitement, pp. 1- 

655, figs. 1-14. 1910. 
Canevari, A. Malattie e Parassiti delle Principali Piante Coltivate, 

pp. 1-374, figs. 1-101. 1913. 
Cooke, M. C. Fungoid pests of cultivated plants, pp. 1-278, pis. 

1-24, figs. 1-23. 1906. 
Delacroix, G. Maladies des plantes cultivees, pp. 1-431, figs. 1-108. 

1908. 



APPENDIX 369 

Ferraris, T. I Parassiti Vegetal! delle piante coltivate od utili. pp. 
1-1032, figs. 1-184. 1913. 

Hartig, R. Wichtige Krankheiten der Waldbaume, pp. 1-127, pis. 
1-6. 1874. 

Hartig, R. Die dureh Pilze erzeugten Krankheiten der Waldbaume, 
pp. 1-24. 1875. 

Hartig, R. Die Zersetzungserscheinungen des Holzes der Nadelholz- 
baume und der Eiehe in forstlieher, botanischer und ehemiseher 
Richtung, pp. 1-151, pis. 1-21. 1878. 

Hartig, R. Untersiichungen aus dem forstbotanisehen Institut zii 
Miinchen. 1 : 1-165, pis. 1-9, figs. 1-2. 1880. 3 : 1-151, pis. 1-11, 
figs. 1-13. 1883. 

Hartig, R. Text-book of the diseases of trees, pp. 1-331, figs. 1-159. 
1894. (English translation of the second German edition, by 
Somerville and Ward.) 

Massee, G. Diseases of cultivated plants and trees, pp. 1-602, figs. 
1-171. 1910. 

Peglion, Vittorio. Le Malattie Crittogamiche delle piante coltivate. 
pp. 1-554. 1912. 

Prillieux, E. Maladies des plantes agricoles. 1:1-421, figs. 1-190; 
2 : 1-592, figs. 191-484. 1895. 

Savastano, L. Patologia arborea applicata, pp. 1-666. 1910. 

Sorauer, P. Handbuch der Pflanzenkrankheiten 2 : 1-550, figs. 
1-62. 1908. 

Sorauer, P. Manual of plant diseases, pp. 1-891, figs. 1-208. (Trans- 
lation of Handbuch der Pflanzenkrankheiten, volume one, by 
Frances Dorranee. Issued in ten parts; not completed.) 

Tubeuf, K. F. von. Beitrage zur Kenntniss der Baumkrankheiten, 
pp. 1-58, pis. 1-5. 1888. 

Tubeuf, K. F. von. Diseases of plants induced by cryptogamie para- 
sites, pp. 1-598, figs. 1-330. 1897. (Translated from the Ger- 
man by W. G. Smith.) 

Voglino, P. Patologia vegetale, pp. 1-287, pis. 1-6, figs. 1-303. 1905. 

Ward, H. M. Timber and some of its diseases, pp. 1-295, figs. 1-45. 
1909. 



Publications on Tree Surgery and the Care of Trees 

Bailey, L. H. The pruning-manual, pp. 88-106. 

Des Cars, A. A treatise on pruning forest and ornamental trees, 
pp. 1-65, figs. 1-53. 1894. 

Fernow, B. E. Care of trees, pp. 1-392, figs. 1-115. 1910. 

Gaskill, A. The planting and care of shade trees. Forest Park Reser- 
vation Commission of New Jersey, pp. 1-128, figs. 1-43. 1912. 

Lodeman, E. G. The spraying of plants, pp. 1-399. 1896. 
2b 



370 APPENDIX 

Mulford, F. L. Pruning and tree-doetoring. In Bailey, Standard 

Cyclopedia of Horticulture, Vol. I, pp. 354-356. 1914. 
Murrill, W. A. Shade trees. Cornell Univ. Agr. Exp. Sta. Bui. 

205 : 73-120. 1902. 
Peets, Elbert. Practical tree repair, pp. 1-265. Illustrated. 1913. 
Solotaroff, W. Shade-trees in towns and cities, pp. 1-287, pis. 1-45, 

figs. 1-35. 1911. 
Taylor, A. D. Shade trees, their care and preservation. Cornell 

Univ. Agr. Exp. Sta. Bui. 256 : 305-345, figs. 223-259. 1908. 
Webster, A. D. Tree wounds and diseases, pp. 1-215. Illustrated. 

1916. 



INDEX 



Abies, see Fir. 

abietina, Melampsoropsis, 315. 
abietinum, Peridermium = Melampso- 
ropsis abietina, 316. 
abietis-canadensis, Cceoma = Melamp- 
sora abietis-canadensis, 182. 

Melampsora, 182, 298. 
acerinum, Rhytisma, 223. 
cesculi, Exoascus, 121. 

Guignardia, 118. 
.(Esculus, see Buckeye. 
aggregata, Erysiphe, 86. 
albertensis, Melampsora, 159, 298. 
albicedrcB, Cyanospora, 204. 
Alder diseases, 86 

brown checked wood-rot, 87 

catkin-deformation, 87 

common white wood-rot, 87. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 
smoke- and, leaves, general, 23. 

late frost-injury, leaves, general, 
21. 

leaf-spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildew, catkins, 86. 
general, 34. 

root-rot, shoe-string, general, 78. 



Alder diseases — Continued 

roots, parasitized by flowering plants, 

general, 84. 
root-tubercles, 88. 
shoe-string root-rot, general, 78. 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, 

general, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
wood-rot, brown checked, 87. 
common white, 87. 
general, 64. 
aini, Microsphara, 153, 241. 

var. extensa, Microsphwra, 241. 
Alnus, see Alder. 
alpina, Melampsora, 343. 
amarus, Polyporus, 135. 
amentorum, Exoascus, 87. 
americana, Razoumofskya, 273. 
annosus, Fomes, 169, 296, 329. 
Anthracnose, see Leaf- and Twig-blight, 

Sycamore or Plane tree, 333. 
apocryptum, Glaeosporiurn, 226. 
Appendix, 361. 
appla^iatus, Fomes, 108, 117, 236, 260, 

310. 

Apples, on juniper, 197. 

Applying wound dressings, 351. 

Arbor-vitse diseases, 89. 

black leaf-spot, 90. 

blight, seedling-, 89. 

leaf-, 90. 
brown pocket heartwood-rot, 91. 
butt-rot, red-brown, 91. 



371 



372 



INDEX 



Arbor-vitse diseases — Continued 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 
freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 
heartwood-rot, brown pocket, 91. 
late frost-injury, leaves, general, 

21. 
leaf-cast of conifers, general, 38. 
leaf-blight, 90. 
leaf-spot, black, 90. 
lightning injury, general, 60. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
red-brown root- and butt-rot, 91. 
root-rot, red-brown, 91. 

shoe-string, general, 78. 
seedling-blight, 89. 
shoe-string root-rot, general, 78. 
smoke- ahd gas-injtiry, leaves, gen- 
eral, 23. 
smothering-disease, seedlings gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
winter-drying, leaves, general, 18. 

seedlings, general, 11. 
wood-rots, general, 64. 
Arceuthobium, see Mistletoe diseases, 
general, 54. 
see Razoumofskya. 
arctica, Melampsora, 159. 
Armillaria mellea, 78. 
Ascochyta piniperda, 313. 
Ash diseases, 93. 

damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 



Ash diseases — Continued 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. ■ 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 
smoke- and, leaves, general, 23. 

heartwood-rot, white, 95. 

late frost-injury, leaves, general, 21. 

leaf- and twig-rust, 93. 

leaf-spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildews, leaves, general, 
34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

rust, leaf- and twig-, 93. 

shoe-string root-rot, general, 78. 

silver-blight, leaves, general, 41. 

silver-leaf, general, 41. 

slime-flux, general, 53. 

smoke- and gas-injury, leaves, gen- 
eral, 23. 

smothering-disease, seedlings, 15. 

sooty molds, leaves, general, 41. 

sun-scald, bark, general, 52. 

sun-scorch, leaves, general, 22. 
seedlings, general, 9. 

twig-rust, leaf- and, 93. 

white heartwood-rot, 95. 

wood-rots, general, 64. 
Asphaltum, briquettes, 356. 

filling for cavities, 356. 

wound dressing, 350. 
Atkinsonii, Uredinopsis, 156. 
aurea, Taphrina, 300. 



Bacillus radicicola, 88, 222. 
hacteriospermus, Exoascus, 112. 
Bacterium tumefaciens, 304. 
Bald cypress diseases, 97. 

body, see Body and branch diseases 
and injuries. 

bot-cypress, 97. 



INDEX 



373 



Bald cypress diseases — Continued 

botty-cypress, 97. 

branch, see Body and branch diseases 
and injuries. 

leaf, see Leaf diseases and injuries. 

peck of cypress, 97. 

pecky heartwood-rot, 97. 

peggy-cypress, 97. 

puck of cypress, 97. 

root, see Root diseases and injuries. 

seedling, see Seedling diseases and 
injuries. 
balsanieum, Peridermium, 156. 
Bark-disease, chestnut, see Endothia 

canker, 140. 
Basal canker, pine, 290. 

heartwood-rot, juniper, 210. 
basicola, Thiclaria, see Daniping-off, 4. 
Basswood diseases, 101. 

damping-ofT, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 

late frost-injury, leaves, general, 21. 

leaf-spot, 102. 

leaf-spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildew, 101. 

powdery mildews, leaves, general, 
34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

root-rot, southern, 103. 

sapwood-rot, white, 103. 

shoe-string root-rot, general, 78. 

silver-blight, leaves, general, 41. 

silver-leaf, general, 41. 

slime-flux, general, 53. 



Basswood diseases — Continued 

smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-diseases, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
southern root-rot, 103. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
white sapwood-rot, 103. 
wood-rots, general, 64. 
Beech di.seases, 105. 

beech-drop, see Parasitized roots, 

108. 
butt-rot, white, 108. 
common wliite wood-rot, 107. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 
freezing-to-death, roots, general, 74. 

seedlings, general, 12. 

twigs and bark, general, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 23. 
late frost-injury, leaves, general, 

21. 
leaf-spots, general, 27. 
lichen-injury, general, 52. 
lightning injury, general, 60. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
parasitized roots, 108. 
powdery mildews, general, 34. 
root-rot, shoe-string, general, 78. 
roots parasitized by flowering plants, 

general, 84. 
sapwood-rot, uniform white, 108. 

yellowish, 105. 
shoe-string root-rot, general, 78. 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 



374 



INDEX 



Beech diseases — Continued 

sooty molds, leaves, general, 41. 

sun-scald, bark, general, 52. 

sun-scorch, leaves, general, 22. 
seedlings, general, 9. 

uniform white sapwood-rot, 108. 

white butt-rot, 108. 

wood-rot, common white, 107. 

wood-rots, general, 64'. 

yellowish sapwood-rot, 105. 
Beech-drop, roots, hjeech, 108. 
Berkeleyi Polyporus, 262. 
bermudianum, Gymnosporangium, 201. 
Betheli, Gymnosporangium, 202. 
Betula, see Birch. 
beiulcB, Melampsoridium, 111, 213. 
betulinus, Polyporus, 113. 
Bibliography of tree diseases, 367. 
Bigelowii, Melampsora, 212, 342. 
Birch diseases, 111. 

blister, red leaf-, 112. 
yellow leaf-, 112. 

brown heartwood-rot, 116. 

butt-rot, white, 117. 

common white wood-rot, 115. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 

heartwood-rot, brown, 116. 

late frost-injury, leaves, general, 
21. 

leaf- rust. 111. 

leaf-spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildews, general, 34. 

powdery sapwood-rot, 113. 

red leaf-blister, 112. 

root-rot, shoe-string, general, 78. 



Birch diseases — Continued 

roots parasitized by flowering plants, 

general, 84. 
rust, leaf-. 111. 
sapwood-rot, powdery, 113. 

yellowish, 115. 
shoe-string root-rot, general, 78. 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, 

general, 23. 
smothering-diseases, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
white butt-rot, 117. 
wood-rot, common wliite, 115. 
wood-rots, general, 64. 
yellow leaf-blister, 112. 
^yellowish sapwood-rot, 115. 
Black leaf-spot, arbor-vitse, 90. 
Black-specked leaf-spot, maple, 225. 
Blasdaleanum, Gymnosporangium, 133. 
Bleeding, set' Slime-flux, 53. 
Blight, brown felt-, cedar, 130. 
pine, 271. 
spruce, 317. 
brown-mold leaf-, hemlock, 180. 
curled leaf- and witches'-broom, 

buckeye, 121. 
felt-, brown, cedar, 130. 
pine, 271. 
spruce, 317. 
gray mold twig-, fir, 161. 
leaf-, arbor-vitse, 89. 
hemlock, 179. 
maple, 228. 
oak, 237. 
plane-tree, 333. 
spruce, 319. 
sycamore, 333. 
leaf- and twig-, spruce, 319. 
leaf-, brown mold, hemlock, 180. 
leaf-, curled and witches'-broom, 

buckeye, 121. 
seedling-, arbor-vitse, 89. 
seedling twig-, spruce, 313. 
silver-, leaves, general, 41. 



INDEX 



375 



Blight — Continued 

twig-, chestnut, 140. 
oak, 244. 
pine, 272. 
plane-tree, 333. 
sycamore, 333. 

twig-, leaf- and, spruce, 319. 

twig-, seedling, juniper, 190. 
spruce, 313. 

twig-, western, cedar, 133. 

western twig-, cedar, 133. 
Blister, leaf-, oak, 239. 

red leaf-, birch, 112. 

yellow leaf-, birch, 112. 
poplar, 300. 
Blister-rust, see under Rust. 
Blueberry rust, leaf, fir, 157. 
Body and branch diseases and injuries, 
45. 

electrical injuries, general, 60. 

freezing-to-death, twigs and bark, 
general, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

lichen-injury, general, 52. 

lightning injuries, general, 60. 

mistletoe diseases, general, 54. 

slime-flux, general, 53. 

sun-scald, general, 52. 

wood-rots, general, 64. 
Bordeaux mixture, 358. 

preparation of, 358. 
boreale, Peridermiutn, 320. 
borealis, Polyporus, 185, 329. 
Bot-cypress, bald cypress, 97. 
botryapiies, Gymnos porangium, 1.34. 
Botrytis, see Damping-off, 4. 
Boirytis cincrea, 161. 

Douglasii = Botrytis cincrea, 161. 
Botty-cypress, bald cypress, 97. 
Branch diseases and injuries, see under 

Body. 
Branch-galls, general, 63. 

juniper, 200. 
Branch-swelling, cedar, 134. 

juniper, 202. 
Brown butt-rot, catalpa, 127. 
Brown checked wood-rot, alder, 87. 

butternut, 124. 

chestnut, 149. 

locust, 221. 



Brown checked wood-rot — Continued 

maple, 232. 

oak, 247. 

walnut, 340. 
Brown felt-blight, cedar, 130. 

pine, 271. 

spruce, 317. 
Brown heart wood-rot, birch, 116. 

fir, 169. 

larch, 216. 

pine, 292. 
Brown mildew, oak, 243. 
Brown-mold leaf-blight, hemlock, 180. 
Brown pocket heartwood-rot, arbor- 
vita?, 91. 

fir, 168. 

hemlock, 184. 

juniper, 204. 

larch, 217. 

pine, 293. 

spruce, 328. 
Brown root- and butt-rot, fir, 169. 

pine, 296. 

spruce, 329. 
Brown wood-rot, elm, 154. 
Buckeye diseases, 118. 

curled leaf-blight and witches'- 
broom, 121. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 

late frost-injury, leaves, general, 21. 

leaf-blight and witches'-broom, 
curled, 121. 

leaf- blotch, 118. 

leaf-spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildew, 121. 



376 



INDEX 



Buckeye diseases — Continued 

powdery mildews, general, 34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

sapwood-rot, white, 122. 

shoe-string root-rot, general, 78. 

silver-blight, leaves, general, 41. 

silver-leaf, general, 41. 

slime-flux, general, 58. 

smoke- and gas-injury, leaves, gen- 
eral, 23. 

smothering-disease, seedlings, gen- 
eral, 15. 

sooty molds, leaves, general, 41. 

sun-scald, bark, general, 52. 

sun-scorch, leaves, general, 22. 
seedlings, general, 9. 

white sapwood-rot, 122. 

witches'-broom, curled leaf-blight 
and, 121. 

wood-rots, general, 64. 
Burls, mistletoe and witches'-broom, 
fir, 163. 

larch, 214. 

pine, 273. 
Butternut diseases, 123. 

brown checked wood-rot, 124. 

common white wood-rot, 124. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 

late frost-injury, leaves, general, 21. 

leaf-spot, 123. 

leaf-spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildews, general, 34. 

root-rot, shoe-string, general, 78. 



Butternut diseases — Continued 

roots parasitized by flowering plants, 

general, 84. 
shoe-string, root-rot, general, 78. 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
wood-rot, brown checked, 124. 

common white, 124. 
wood-rots, general, 64. 
Butt-rot, brown, catalpa, 127. 

fir, 169. 

pine, 296. 

spruce, 329. 
red-brown, arbor- vitse, 91. 

fir, 170. 

hemlock, 187. 

larch, 217. 

pine, 294. 

spruce, 331. 
straw-colored, oak, 259. 
string and ray, oak, 252. 
white, beech, 108. 

birch, 117. 

maple, 236. 

oak, 260. 

poplar, 310. 
white piped, chestnut, 150. 

oak, 258. 



Cwoma ahietis-canadensis = Melamp- 
sora ahietis-canadensis, 182. 

occidentalis = Melampsora alber- 

tensis, 159. 
Calyptospora columnaris, 157. 
campanuloe, Caleosporium, 268. 
campylopoda, Razoumofskya, 273. 
Canker, basal, pine, 290. 

Endothia, chestnut, 140. 

eradication, 346, 351. 

excision for control of, 351. 

maple, 229. 



INDEX 



377 



Canker — Continued 

poplar, 301. 

pruning for control of, 346. 

Strumella, chestnut, 148. 
oak, 245. 
Capping wounds, 350. 
carnea, Taphrina, 112. 
carneus, Polyporus = Fomes roseus, 

204. 
Carya, see Hickory. 
cassandrce, Melampsoropsis, 315. 
Castanea, see Chestnut. 
Castilleja rust, pine, 285. 
Catalpa diseases, 125. 

brown butt-rot, 127. 

butt-rot, brown, 127. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 

late frost-injury, leaves, general, 21. 

leaf-spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildews, general, 34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

shoe-string root-rot, general, 78. 

silver-blight, leaves, general, 41. 

silver-leaf, general, 41. 

slime-flux, general, 53. 

smoke- and gas-injury, leaves, gen- 
eral, 23. 

smothering-disease, seedUngs, gen- 
eral, 15. 

sooty molds, leaves, general, 41. 

sun-scald, bark, general, 52. 

sun-scorch, leaves, general, 22. 
seedlings, general, 9. 



Catalpa diseases — Continued 
wood-rot, yellowish, 125. 
wood-rots, general, 64. 
yellowish wood-rot, 125. 
catalpcE, Polyporus, 127. 

Poria = Polyporus catalpoe, 127. 
Catkin-deformation, alder, 87. 

poplar, 301. 
Cavity treatments, 353. 
Cedar-apples, juniper, 197. 
Cedar diseases, 129. 

blight, brown felt-, 130. 

western twig-, 133. 
branch-swelling, 134. 
brown felt-bhght, 130. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
dry-rot, 135. 
eastern leaf -rust, 129. 

witches'-broom, 131. 
electrical injuries, general, 60. 
felt-blight, brown, 130. 
freezing-to-death, roots, general, 74. 

seedlings, general, 12. 

twigs and bark, general, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 
heartwood-rot, pecky, 135. 
late frost-injury, leaves, general, 21. 
leaf-rust, eastern, 129. 

western, 130. 
leaf-spots, general, 27. 
lichen-injury, general, 52. 
lightning injury, general, 60. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
peckiness, 135. 
pecky heartwood-rot, 135. 
pin-disease, 135. 
pin-rot, 135. 

powdery mildews, general, 34. 
root-rot, shoe-string, general, 78. 
roots parasitized by flowering plants, 

general, 84. 
rot, dry-, 135. 

pin-, 135. 



378 



INDEX 



Cedar diseases — Continued 
rust, eastern leaf-, 129. 

western leaf-, 130. 
shoe-string root-rot, general, 78. 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke-and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
twig-blight and witches' -broom, 

western, 133. 
western leaf-rust, 130. 

twig-blight and witches' -broom, 
133. 
winter drying, leaves, general, 18. 

seedlings, general, 11. 
witches'-broom, eastern, 131. 

western twig-blight and, 133. 
wood-rots, general, 64. 
Celtis, aee Hackberry. 
Cenangium ferruginosum, 272. 
Cercospora, see Leaf-spots, 27. 
Cercospora tilice, 102. 
cerebrum, Cronartium, 287. 

Peridermium = Cronartium cere- 

brum,, 287. 
Chamsecyparis, see Cedar. 
Chestnut-blight, chestnut, 140. 
Chestnut diseases, 138. 

bark-disease, see Endothia canker, 

140. 
blight, see Endothia canker, 140. 
brown checked wood-rot, 149. 
butt-rot, white piped, 150. 
canker, Endothia, 140. 

Strumella, 148. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 
Endothia canker, 140. 
freezing-to-death, roots, general, 
74. 
seedlings, general, 12. 



Chestnut diseases — Continued 
twigs and bark, general, 47. 
freezing-to-death, frost-cracks, gen- 
eral, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 23. 
heartwood-rot, straw-colored, 149. 
large leaf-spot, 139. 
late frost-injury, leaves, general, 

21. 
leaf-spot, large, 139. 
leaf-spots, general, 27. 
lichen-injury, general, 52. 
lightning injury, general, 60. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
powdery mildews, general, '34. 
root-rot, shoe-string, general, 78. 
roots parasitized by flowering plants, 

general, 84. 
shoe-string root-rot, general, 78. 
silver- blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
straw-colored heartwood-rot, 149. 
Strumella canker, 148. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
twig-blight, 140. 
white piped butt-rot, 150. 
wood-rot, brown checked, 149. 
wood-rots, general, 64. 
Chryso7ny.ra Weirii, 316. 
cinerea, Botrytis, 161. 
cinnabarina, Nectria, 229. 
circinata, Uncinula, 227. 
clavariceforme, Gymnosporangium, 203. 
Clintonii, Uncinula, 101. 
ccerulescens, Taphrina, 239. 
coleosporioides, Cronartium, 285. 
Coleosporium, see Leaf blister-rusts, 

pine, 265. 
Coleosporium campanulce, 268. 
delicatulum, 268. 



INDEX 



379 



Coleosporium — Continued 
elephantopodis, 267. 
helianihi, 269. 
inconspicuum, 266. 
ipomcece, 268. 
ribicola, 269. 
solidaginis, 267. 
sonchi-arvensis, 266. 
terebinthinaceae, 269. 
vernonice, 267. 
Colletotrichum, see Damping-off, 4. 
Collybia velutipes, 103, 122. 
coloradense, Peridermium, 320. 
columnar e, Peridermium = Calypto 

spora columnaris, 157. 
columnaris, Calyptospora, 157. 
Comandra rust, pine, 283. . 
comandrce, Cronartium, 283. 
Common names of trees, 361. 
Common white wood-rot, alder, 87. 
beech, 107. 
birch, 115. 
butternut, 124. 
hickory, 189. 
maple, 232. 
oak, 250. 
poplar, 305. 
walnut, 339. 
willow, 343. 
comptonice, Cronartium, 281. 

Peridermium = Cronartium compto- 
nice, 281. 
Concrete, filling for cavities, 355. 
Cone- and twig-rusts, leaf-, hemlock, 

182. 
Cone blister-rusts, leaf and, hemlock, 

180. 
Cone-rust, spruce, 320. 
confluens, Melampsora, 343. 
Conifer, leaf-cast, general, 38. 
consimile, Peridermium = Melamp- 

soropsis cassandrw, 315. 
corniculans, Gymnosporangium, 202. 
cornutum, Gymnosporangium, 203. 
corylea, Phyllactinia, 153, 227 241 

341. 
coryneoidea, Strumella, 148, 245. 
Coulteri, Ncopeckia, 271. 
Cracking-scurf, see Leaf-cast of conifers, 

general, 38. 
croceus, Polyporus, 150, 258. 



Cronartium cerebrum, 287. 

coleosiJorioides, 285. 

comandrce, 283. 

comptonice, 281. 

.occidentale, 290. 

ribicola, 274. 
Cuboidal wood-rot, hemlock, 185. 

spruce, 329. 
Curled leaf-blight and witches'-broom, 

buckeye, 121. 
Cyanospora albicedrce, 204. 
cydoniw, Physalospora = Sphceropsis 

malorum, 140, 244. 
Cylindrosporium, see Leaf-spots, 27. 
Cypress, see Bald cypress. 

D 

Damping-off, seedlings, general, 2. 

Davisii, Gymnosporangium, 196. 

debaryanum, Pythium, 3. 

decolorans, Peridermium — Melampso- 
ropsis ledicola, 315. 

deformans, Hypoderma, 271. 

delicatulum, Coleosporium, 268. 

Desmazierii, Monochcetia, 139, 243. 

Diaporthe parasitica = Endothia para- 
sitica, 140. 

Disinfectants for wounds, 348. 

Disinfecting wounds, 348. 

Dothichiza populea, 301. 

Douglasii, Botrytis = Botrytis cinerea 
161. 
Razoumofskya, 163. 

Dressings, wound, 348. 

Drought-injury and sun-scorch, leaves, 
general, 22, 

Drowning, drying and, roots, general, 
73. 

dryadeus, Polyporus, 261. 

dryophilus, Polyporus = Polyporus 

Rheades, 250, 310. 

Drying and drowning, roots, 73. 

Dry-rot, cedar, 135. 

Dusting for leaf diseases, spraying and, 
357. 

E 

Earlei, Fames, 208. 
Eastern leaf-rust, cedar, 129. 
witches'-broom, cedar, 131. 



380 



INDEX 



Echinodontium tinctorium, 166, 184, 

328. 
cffusum, Gymnosporangium, 203. 
elatina, Melampsorella, 160. 
Electrical injuries, 60. 
elephantopodis, Coleosporium, 267. 
EUisianus, Polyporus, 293. 
Elm diseases, 152. 

brown wood-rot, 154. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, general, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 
smoke- and, leaves, general, 23. 

late frost-injury, leaves, general, 21. 

leaf-spot, 152. 

leaf -spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildews, 153. 

powdery mildews, general, 34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

shoe-string root-rot, general, 78. 

silver-blight, leaves, general, 41. 

silver-leaf, general, 41. 

slime-flux, general, 53. 

smoke- and gas-injury, leaves, gen- 
eral, 23. 

smothering-diseases, seedlings, gen- 
eral, 15. 

sooty molds, leaves, general, 41. 

sun-scald, bark, general, 52. 

sun-scorch, leaves, general, 22. 
seedlings, general, 9. 

wood-rot, brown, 154. 

wood-rots, general, 64. 
Endothia canker, chestnut, 140. 
Endothia parasitica, 140. 
Epiphegus virginiana, 108. 
Equipment, pruning, 346. 



Eradication, see Pruning, 346. 

see Lesion excision, 351. 
erinaceus, Hydnum, 254. 
Erysiphacese, see Powdery mildews, 

general, 34. 
Erysiphe aggregata, 86. 

trina, 241. 
Everhartii, Fames, 260. 
exiguum, Gymnosporangium, 196. 
Exoascus cesculi, 121. 

amentorum, 87. 

bacteriospermus, 112. 
exterum, Gymnosporangium, 203. 



F 



Fagus, see Beech. 
Farlowii, Necium, 182. 
Felt-blight, brown, cedar, 130. 

pine, 271. 

spruce, 317. 
Felt-rust, currants and gooseberries, 

278. 
Fern rust, leaf, fir, 156. 
ferruginosum, Cenangium, 272. 
filamentosum, Peridermium = Cronar- 

tium coleosporioides, 285. 
Filling cavities, 355. 
Fir diseases, 155. 

blight, gray mold twig-, 161. 

blister-rusts, see Leaf blister-rusts. 

blueberry rust, 157. 

brown heartwood-rot, 169. 

brown pocket heartwood-rot, 168. 

brown root- and butt-rot, 169. 

burl, mistletoe and witches'-broom, 
163. 

butt-rot, brown, 169. 
red- brown, 170. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

fern rust, 156. 

fireweed rust, 157. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, 47. 

frost-cracks, general, 50. 

galls, general, 63. 



INDEX 



381 



Fir diseases — Continued 

gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 
gray mold twig-blight, 161. 
heartwood-rot, brown, 169. 

brown pocket, 168. 

stringy red-brown, 166. 
late frost-injury, leaves, general, 

21. 
leaf blister-rusts, 155. 

blueberry rust, 157. 

fern rust, 156. 

fireweed rust, 157. 

unconnected rusts, 158. 
leaf-cast, 159. 

of conifers, general, 38. 
leaf-rusts, 159. 

poplar rust, 159. 

willow rust, 159. 
lightning injury, general, 60. 
mistletoe burl and witches'-broom, 

163. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
pecky wood-rot, 163. 
poplar rust, 159. 

red-brown root- and butt-rot, 170. 
red-brown sapwood-rot, 165. 
root-rot, brown, 169. 

red- brown, 170. 

shoe-string, 78. 

yellow, 170. 
rusts, sec Leaf-rusts and Leaf blister- 
rusts, 
rust witches'-broom, 160. 
sapwood-rot, red-brown, 165. 
shoe-string root-rot, general, 78. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
stringy red-brown heartwood-rot, 

166. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
twig-blight, gray mold, 161. 
unconnected rusts, 158. 
willow rust, 159. 



Fir diseases — Continued 

winter-drying, leaves, general, 18. 

seedlings, general, 11. 
witches'-broom, mistletoe burl and, 
163. 
rust, 160. 
wood-rot, pecky, 163. 
wood-rots, general, 64. 
yellow root-rot, 170. 
Fireweed rust, leaf, fir, 157. 
Five-needle pine blister-rust, 274. 
flava, Magnusiella, 112. 
flexuosa, Uncinula, 121. 
floriforme, Gyynnosporangium, 201. 
Flowering plants, roots parasitized by, 

84. 
fomentarius, Fonies, 105, 115. 
Fames annosus, 169, 296, 329. 

applanatus, 108, 117, 230, 260, 310. 

Earlei, 208. 

Evcrhartii, 260. 

fomentarius, 105, 115. 

fraxinophilus, 95. 

fulvus, 116. 

geotropus, 97. 

igniarius, 87, 107, 115, 124, 189, 

232, 250, 305, 339, 343. 
juniperinus, 206, 208. 
laricis, 169, 216, 292. 
nigricans, 305. 
officinalis, 169, 216, 292. 
pinicola, 165, 184, 215, 292, 327. 
rimosus, 219. 
roseus, 91, 168, 184, 204, 217, 293, 

328. 
texanus, 209. 
fragile, Peridcrmium, 269. 
fraternum, Gymnosporangium, 129. 
fraxinata, Puccinia, 93. 
fraxinophilus, Fomes, 95. 
Fraxinus, see Ash. 
Freezing-to-death, roots, 74. 
seedlings, 12. 
twigs and bark, 47. 
frondosus, Polyporus, 149, 259. 
Frost-cracks, general, 50. 
Frost injuries, see Temperature injuries. 
Frost-injury, late, leaves, 21. 
Fuckeliana, Sclerotijiia = Bctryiis 

cinerea, 161. 
funerea, Pestalozzia, 319. 



382 



INDEX 



fructigenum, Peridermium = Melamp- 
sora abietis-canadensis, 182. 

fulvus, Fomes, 116. 

fusiforme, Peridermium = Cronartium 
cerebrum,, 287. 

G 

Gallowaya pini, 270. 
Galls, branch-, juniper, 200. 
general, 63. 
limb-, poplar, 304. 
Gas-injury, roots, general, 76. 
Gas-injury, smoke- and, leaves, general, 

23. 
geotropus, Fomes, 97. 
germinale, Gymnosporangium, 202. 
globosum, Gymnosporangium, 197. 
Gloeosporium, leaf-blight, maple, 228. 

see Leaf-spots, general, 27. 
Gloeosporium apocryptum, 226. 

nervisequum, 336. 
Glossary, 365. 

Gnomonia leptostyla = Marssonia jug- 
landis, 123. 

ulmea, 152. 

veneta, 237, 333. 
gracile7is, Gymnosporangium, 203. 
Gray mold twig-blight, fir, 161. 
Gray-rot, see Red-ray wood-rot, pine, 

293. 
Guignardia cesculi, 118. 
Gymnosporangium, leaf- and stem- 
rusts (general), 192. 
Gymnosporangium bermudianum, 201. 

Betheli, 202. 

Blasdaleanum, 133. 

boiryapites, 134. 

clavarioe forme, 203. 

corniculans, 202. 

cornutum, 203. 

Davisii, 196. 

effusum, 203. 

exiguum, 196. 

exterum, 203. 

fraternum, 129. 

floriforme, 201. 

germinale, 202. 

globosum, 197. 

gracilens, 203. 

inconspicuum., 196. 

juniperinum, 201. 



Gymnosporangium — Continued 
juniperi-virginiance, 197. 
juvenescens, 200. 
Kernianum, 200. 
koreaense, 196. 
multiporum, 196. 
myricatum, 131. 
Nelsoni, 202. 
Nidus-avis, 200. 
nootkatensis, 130. 
trachysorum, 201. 

H 

Hackberry diseases, 173. 

damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 
freezing-to-death, roots, general, 74. 

seedlings, general, 12. 

twigs and bark, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 23. 
late frost-injury, leaves, general, 

21. 
leaf-spots, general, 27. 
lichen-injury, general, 52. 
lightning injury, general, 60. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
powdery mildews, 173. 

general, 34. 
root-rot, shoe-string, general, 78. 
roots parasitized by flowering plants, 

general, 84. 
shoe-string root-rot, general, 78. 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 



INDEX 



383 



Hackberry diseases — Continued 
witches'-broom, 174. 
wood-rots, general, 64. 
Harknessii, Peridermium; see Cronar- 
tiurn coleosporioides , 285. 
see Cronartium cerebrum, 287. 
Heartwood-rot, basal, juniper, 210. 
brown, birch, 116. 

fir, 169. 

larch, 216. 

pine, 292. 
brown pocket, arbor- vitie, 91. 

fir, 168. 

hemlock, 184. 

juniper, 204. 

larch, 217. 

pine, 29.3. 

spruce, 328. 
cavity treatments, surgery, 353. 
disinfecting wounds, surgery, 348. 
general, 64. 
honeycomb, oak, 255. 
lesion excision, surgery, 351. 
pecky, bald cypress, 97. 

cedar, 135. 
soft, oak, 257. 

straw-colored, chestnut, 149. 
stringy red-brown, fir, 166. 

hemlock, 184. 

spruce, 328. 
tree surgery, 345. 
wet, oak, 254. 
white, ash, 95. 
white pocket, juniper, 206. 

oak, 250. 

poplar, 310. 
wound dressings, surgery, 348. 
Heartwood-rot, see Sapwood-rot. 

see Wood-rot. 
helianthi, Coleosporium, 269. 
Hemlock diseases, 177. 

brown-mold leaf-blight, 180. 
brown pocket heartwood-rot, 184. 
butt-rot, red-brown root- and, 187. 
cone blister-rusts, leaf and, 180. 
cone- and twig-rust, leaf-, 182. 
cuboidal wood-rot, 185. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 



Hemlock diseases — Continued 
electrical injuries, general, 60. 
freezing-to-death, roots, general, 74. 

seedlings, general, 12. 

twigs and bark, general, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 
heartwood-rot, brown pocket, 184. 

stringy red-brown, 184. 
late frost-injury, leaves, general, 21. 
leaf and cone blister-rusts, 180. 
leaf-blight, 179. 

brown mold, 180. 
leaf-cast of conifers, general,. 38. 
leaf-, cone- and twig-rust, 182. 
lightning injury, general, 60. 
mistletoe di-seases, general, 54. 
mycorhizas, roots, general, 82. 
red-brown root- and butt-rot, 187. 

sapwood-rot, 184. 
root-rot, seedlings, 177. 

shoe-string, general, 78. 
root- and butt-rot, red-brown, 187. 
sapwood-rot, red-brown, 184. 
shoe-string root-rot, general, 78. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
stringy red-brown heartwood-rot, 

184. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
twig-rust, leaf-, cone- and, 182. 
winter-drying, leaves, general, 18. 

seedlings, general, 11. 
wood-rot, cuboidal, 185. 
wood-rots, general, 64. 
Herpotrichia nigra, 130, 317. 

quinqueseptata, 317. 
Hickory diseases, 188. 

common white wood-rot, 189. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 



384 



INDEX 



Hickory diseases — Continued 
electrical injuries, general, 60. 
freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 
late frost-injury, leaves, general, 21. 
leaf-mildew and witches'-broom, 188. 
leaf-spots, general, 27. 
lichen-injury, geiaeral, 52. 
lightning injury, general, 60. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
powdery mildews, general, 34. 
root-rot, shoe-string, general, 78. 
roots parasitized by flowering plants, 

general, 84. 
shoe-string root-rot, general, 78. 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
witches'-broom, leaf-mildew and, 

188. 
wood-rot, common white, 189. 
wood-rots, general, 64. 
Hicoria, see Hickory. 
Holwayi, Peridermmm, 158. 
Honeycomb heartwood-rot, oak, 255. 
Honey-mushroom root-rot, 78. 
Horse-chestnut diseases, see Buckeye 

diseases, 118. 
Hydnum seplentrionale, 108, 234. 

erinaceus, 254. 
Hymeniales, see Wood-rots, general, 64. 
Hypoderma,see Leaf-cast of conifers, 38. 
Hypoderma strobicola, 270. 

deformans, 271. 
Hypodermella, see Leaf-cast of conifers, 
38, 



igniarius, Fomes, 87, 107, 115, 124, 

189, 232, 250, .305, 339, 343. 
Illuminating gas, see Gas-injury, roots, 

76. 
inconspicuum, Coleosporium, 266. 

Gymnosporangium, 196. 
Injuries, drought-, leaves, 22. 
drowning, roots, 73. 
drying, roots, 73. 
electrical, 60. 

freezing-to-death, roots, 74. 
seedlings, 12. 
twigs and bark, 47. 
frost-cracks, 50. 
frost, leaves, 21. 
gas-, roots, 76. 

smoke- and, leaves, 23. 
late frost-, leaves, 21. 
lichen-, 52. 
lightning, 60. 

smoke- and gas-, leaves, 23. 
sun-scald, twigs and bark, 52. 
sun-scorch, leaves, 22. 

seedlings, 9. 
\vinter-drying, leaves, 18. 
seedlings, 11. 
'ntcrmediutn, Peridermium, 267. 
Ipomoece, Coleosporium, 268. 

J 

Joliansonii, Taphrina, 301. 
jtiglandis, Marssonia, 123, 339. 

Microstroma, 188. 
Juglans, see Butternut and Walnut. 
.Juniper diseases, 190. 

apples, cedar-, 197. 

basal heartwood-rot, 210. 

blight, seedling, twig-, 190. 

branch-galls, 200. 

branch-swellings, fusiform, 202. 

brown pocket heartwood-rot, 204. 

cedar-apples, 197. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, 47. 



INDEX 



385 



Juniper diseases — Continued 
frost-cracks, general, 50. 
fusiform, branch-swellings, 202. 
galls, branch-, 200. 

general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 23. 
heartwood-rot, basal, 210. 

brown pocket, 204. 

white pocket, 206. 
late frost-injury, leaves, general, 

21. 
leaf- and stem-rusts (general), 192. 
leaf- and twig-rusts, 196. 
leaf-cast of conifers, general, 38. 
lightning injury, general, 60. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
root-rot, shoe-string, general, 78. 
rust witches'-brooms, 200. 
rusts, apples, cedar-, 197. 

branch-swellings, fusiform, 202. 

cedar-apples, 197. 

fusiform, branch-swellings, 202. 

galls, branch-, 200. 

leaf- and stem- (general), 192. 

leaf- and twig-, 196. 

stem-, leaf- (general), 192. 

swellings, fusiform, branch-, 202. 

twig-, and leaf- and, 196. 

witches'-broom, 200. 
seedling twig-blight, 190. 
shoe-string root-rot, general, 78. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
stem-rusts, leaf- and (general), 192. 
stringy brown wood-rot, 209. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
swellings, fusiform, branch-, 202. 
twig-blight, seedling, 190. 
twig-rusts, leaf- and, 196. 
white bark, 204. 

white pocket heartwood-rot, 206. 
winter-drying, leaves, general, 18. 

seedlings, general, 11. 
witches'-brooms, rust, 200. 

2c 



Juniper diseases — Continued 
wood-rot, stringy brown, 209. 

yellow, 208. 
wood-rots, general, 64. 
yellow wood-rot, 208. 

junipcrinum, Gymnosporangium, 201. 

juniperinus, Fomes, 206, 208. 

juniperi-virginiancB , Gymnosporangium, 
197. 

Juniperus, see Juniper. 

juvenescens, Gymnosporangium, 200. 

K 

Keithia thujina, 90. 

tsugce, 179. 
Kernianum, Gymnosporangium, 200. 
koreaense, Gymnosporangium, 196. 



laciniata, Thelcphora, 15. 
lancstris, Sphwrotheca, 243. 
Larch diseases, 212. 

brown heartwood-rot, 216. 
brown pocket heartwood-rot, 217. 
burl and witches'-broom, mistletoe, 

214. 
butt-rot, red-brown root- and, 217. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 
freezing-to-death, roots, general, 74. 

seedlings, general, 12. 

twigs and bark, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 23. 
heartwood-rot, brown, 216. 

brown pocket, 217. 
late frost-injury, leaves, general, 21. 
leaf-cast of conifers, general, 38. 
leaf-rusts, 212. 
lightning injury, general, 60. 
mistletoe burl and witches'-Vjroom, 

214. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
pccky wood-rot, 215. 
red-brown root- and butt-rot, 217. 



386 



INDEX 



Larch diseases — Continued 
red-brown sapwood-rot, 215. 
root- and butt-rot, red-brown, 217. 
root-rot, seedlings, 212. 
shoe-string, general, 78. 
yellow, 218. 
rusts, leaf-, 212. 
sapwood-rot, red-brown, 215. 
seedling root-rot, 212. 
shoe-string root-rot, general, 78. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
winter-drying, leaves, general, 18. 

seedlings, general, 11. 
witches'-broom, mistletoe burl and, 

214. 
wood-rot, pecky, 215. 
wood-rots, general, 64. 
yellow root-rot, 218. 
Large leaf-spot, chestnut, 139. 
laricis, Fames = Fames afficinalis, 169, 
216, 292. 
Razoumofskya, 214. 
Late frost-injury, leaves, general, 21. 
Leaf and cone blister-rusts, hemlock, 

180. 
Leaf- and twig-rust, ash, 93. 

juniper, 196. 
Leaf-blight, arbor-vitse, 90. 
hemlock, 179. 
brown-mold, hemlock, 180. 
maple, 228. 
oak, 237. 
plane-tree, 333. 
spruce, 319. 
sycamore, 333. 
Leaf-blister, oak, 239. 
yellow, birch, 112. 
poplar, 300. 
Leaf blister-rusts, fir, 155. 
pine, 265. 
spruce, 315. 
Leaf-blotch, buckeye, 118. 
Leaf-browning, see Leaf-cast of conifers, 
general, 38. 



Leaf-cast, fir, 159. 

western yellow pine, 271. 

white pine, 270. 
Leaf-cast of conifers, general, 38. 

host index to, 40. 
Leaf-, cone- and twig-rusts, hemlock, 

182. 
Leaf diseases and injuries, 17. 

drought-injury, general, 22. 

gas-injury, smoke- and, general, 23. 

late frost-injury, general, 21. 

leaf-cast of conifers, general, 38. 

leaf-spots, general, 27. 

powdery mildews, general, 34. 

silver- blight, general, 41. 

silver-leaf, general, 41. 

smoke- and gas-injury, general, 23. 

sooty molds, general, 41. 

sun-scorch, general, 22. 

winter-drying, general, 18. 
Leaf-mildew and witches'-broom, 

hickory, 188. 
Leaf-reddening, see Leaf-cast of conifers, 

general, 38. 
Leaf -rust, birch. 111. 

eastern, cedar, 129. 

western, cedar, 130. 

fir, 159. 

juniper (general) 192. 

larch, 212. 

pine, 270. 

poplar, 298. 

spruce, 316. 

willow, 341. 
Leaf-spot, basswood, 102. 

black-specked, maple, 225. 

butternut, 123. 

drought-injury, 22. 

elm, 152. 

gas-injury, 23. 

large, chestnut, 139. 
oak, 243. 

linden, 102. 

maple, 223, 225, 226. 

powdery mildews, as indexed, 
general, 34. 

silver- blight, 41. 

silver-leaf, 41. 

smoke-injury, 23. 

sooty mold, 41. 
I sun-scorch, 22. 



INDEX 



387 



Leaf -spot — Continued 

tar, maple, 223. 
willow, 343. 

walnut, 339. 

willow, 343. 
Leaf-spots, fungi causing, 28. 

general, 27. 

host index to, 28. 
ledicola, Melampsoropsis, 315. 
leptostyla Gnomonia = Marssonia ju- 

glandis, 123. 
Lesion excision, 351. 
Libocedrus, see Cedar. 
Lichen-injury, general, 52. 
Lightning, sec Electrical injuries, 60. 
Limb-gall, poplar, 304. 
Lime-sulfur, 358. 
Linden, see Basswood. 
Locust diseases, 219. 

brown checked wood-rot, 221. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 
smoke- and, leaves, general, 23. 

late frost-injury, leaves, general, 21. 

leaf -spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildews, general, 34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

root-tubercles, 222. 

shoe-string root-rot, general, 78. 

silver-blight, leaves, general, 41. 

silver-leaf, general, 41. 

slime-flux, general, 53. 

smoke- and gas-injury, leaves, gen- 
eral, 23. 

smothering-disease, seedlings, gen- 
eral, 15. 



Locust diseases — Continued 

sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
wood-rot, brown checked, 221. 

yellow, 219. 
wood-rots, general, 64. 
yellow wood-rot, 219. 
Lophodermium, see Leaf-cast of coni- 
fers, general, 38. 
Lophodermium nervisequum, 159. 

M 

macrospora, Uncinula, 153. 
Magnusiella flava, 112. 
malorum, Sphceropsis, 140, 244. 
Maple diseases, 223. 

black-specked leaf-spot, 225. 

brown checked wood-rot, 232. 

butt-rot, white, 236. 

canker, 229. 

common white wood-rot, 232. 

damping-off, seedlings, gejieral, 2. 

drought-injurj^ leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 00. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 
smoke- and, leaves, general, 23. 

late frost-injury, leaves, general, 21. 

leaf-blight, 228. 

leaf-spot, black-specked, 225. 
tar, 223. 

leaf-spots, 226. 
general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildews, 227. 
general, 34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

sapwood-rot, uniform white, 234. 



388 



INDEX 



Maple diseases — Continued 

sapwood-rot, white streaked, 235. 

shoe-string root-rot, general, 78. 

silver-blight, leaves, general, 41. 

silver-leaf, general, 41. 

slime-flux, general, 53. 

smoke- and gas-injury, leaves, gen- 
eral, 23. 

smothering-disease, seedlings, gen- 
eral, 15. 

sooty molds, leaves, general, 41. 

sun-scald, bark, general, 52. 

sun-scorch, leaves, general, 22. 
seedlings, general, 9. 

tar leaf-spot, 223. 

uniform white sapwood-rot, 234. 

white butt-rot, 236. 

white strand wood-rot, 233. 
streaked sapwood-rot, 235. 

wilt, 231. 

wood-rot, brown checked, 232. 
common white, 232. 
white strand, 233. 

wood-rots, general, 64. 
Marssonia juglandis, 123, 339. 
Marssonia, see Leaf-spots, general, 

27. 
Medusce, Alelampsora, 212, 298. 
Melampsora abietis-canadensis, 182, 
298. 

albcrtensis, 159, 298. 

alpina, 343. 

arctica, 159. 

Bigelowii, 212, 342. 

confluens, 343. 

MeduscB, 212, 298. 
Melampsorella elatina, 160. 
Alelampsoridium betulm, 111, 213. 
Melampsoropsis abietina, 315. 

cassandrce, 315. 

ledicola, 315. 

pyrolce, 320. 
mellea, Armillaria, 78. 
Microsphwra alni, 153, 241. 

alni var. extensa, 241. 
Microstroma juglandis, 188. 
Mildew, see Powdery mildew. 
minima, Phyllosticta, 226. 
■minimum, Pucciniastrum.,. 180. 
minutum, Peridertnium., 269. 
mirabilis, Uredinopsis, 156. 



Mistletoe burl and witches'-broom, 
fir, 163. 

larch, 214. 

pine, 273. 
Mistletoe diseases, general, 54. 

host index to, 55, 57. 
Mistletoe witches'-broom, spruce, 321. 
Monochcetia Desmazierii, 139, 243. 
montanu7n, Periderm,ium,, 267. 
muUiporum, Gymnosporangium, 196. 
Mycorhizas, roots, general, 82. 
myricatum, Gymnosporangium,, 131. 
myrtilli, Pucciniastrum, 180. 

N 

Necium Farlowii, 182. 
Nectria cinnabarina, 229. 
Nelsoni, Gymnosporangium, 202. 
Neopeckia Coulteri, 271. 
nerviscquum, Glwosporium = Gnom,onia 
veneta, 333. 
Lophodermium, 159. 
Nidus-avis, Gymnosporangium, 200. 
nigra, Herpotrichia, 130, 317. 
nigricans, Fomes = Fames igniarius, 305. 
nootkatensis , Gymnosporangium,, 130. 

O 

Oak diseases, 237. 
blight, leaf, 237. 

twig-, 244. 
blister, leaf-, 239. 
l)rown checked wood-rot, 247. 
brown mildew, 243. 
butt-rot, straw-colored, 259. 

string and ray, 252. 

white, 260. 

white piped, 258. 
canker, Strumella, 245. 
common white wood-rot, 250. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 
freezing-to-death, roots, general, 
74. 

seedlings, general, 12. 

twigs and bark, 47. 
frost-cracks, general, 50. 



INDEX 



389 



Oak diseases — Continued 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 
23. 
heartwood-rot, honeycomb, 255. 

soft, 257. 

wet, 254. 

white pocket, 250. 
honeycomb heartwood-rot, 255. 
large leaf-spot, 243. 
late frost-injury, leaves, general, 

21. 
leaf-blight, 237. 
leaf-blister, 239. 
leaf-spot, large, 243. 
leaf-spots, general, 27. 
lichen-injury, general, 52. 
lightning injury, general, 60. 
mildew, brown, 243. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
powdery mildews, 241. 

general, 34. 
root-rot, shoe-string, general, 78. 

white, 261. 
roots parasitized by flowering plants, 

general, 84. 
shoe-string root-rot, general, 78. 
sUver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
soft heartwood-rot, 257. 
sooty-molds, leaves, general, 41. 
straw-colored butt-rot, 259. 
string and ray butt-rot, 252. 
Strumella canker, 245. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
twig-blight, 244. 
wet heartwood-rot, 254. 
white butt-rot, 260. 
white piped butt-rot, 258. 
white pocket heartwood-rot, 250. 
white root-rot, 261. 
white wood-rot, 260. 



Oak diseases — Continued 

wood-rot, brown checked, 247. 
common white, 250. 
white, 260. 
wood-rots, general, 64. 

Oak rust, pine, 287. 

obtusus, Polyporus, 257. 

occidentale, Cronartiuni, 290. 

occidentalis, CcBoma = Melampsora al- 
bertensis, 159. 

officinalis, Fomcs, 169, 216, 292. 

omnivora, Phytophthora, 4. 

Open cavity treatment, 353. 

ornamentale, Peridermium, 158. 

osniundce, Uredinopsis, 156. 

osfreatus, Pleurotus, 235. 

Ozonium, see Southern root-rot, 103. 



parasitica, Diaporthc = E ndothia parasit- 
ica, 140. 
parasitica, Endothia, 140. 
Parasitized by flowering plants, roots, 

84. 
Parasitized roots, beech, 108. 
parvula, Uncinula, 173. 
Peck of cypress, bald cypress, 97. 
Peckii, Peridcrmiuvi = Pucciniastrum 
minimum and Pucciniastrum 
mrjrtilli, 180. 
Peckiness, cedar, 135. 

fir, 163. 

sec Pecky wood-rot. 
Pecky heartwood-rot, bald cyi:>ress, 97. 

cedar, 135. 
Pocky wood-rot, fir, 163. 

larch, 215. 

pine, 291. 

spruce, 324. 
''cggy-cypress, bald cypress, 97. 
Peridermium abietinum., 316. 

balsameum, 156. 

boreale, 320. 

cerebrum, 288. 

coloradense, 320. 

culumnare = Calyptospora culumnaris, 
157. 

comptonice, 282. 

consimilc, 316. 

decolorans, 316. 

filamentosum, 286. 



390 



INDEX 



Peridermium — Continued • 
fragile, 269. 
fructigenum, 182. 
Harknessii, 286, 288. 
Holwayi, 158. 
intermedium, 267. 
minutum, 269. 
■montanum, 267. 
omamentale, 158. 
Pecfcw, 181. 

pseudo-balsameum, 156. 
pyriforme, 284. 
s^robi", 279. 
Perisporiacese, see Sooty molds, 41. 
Pestalozzia funerea, 319. 
phegopteridis , Uredinopsis, 156. 
Phoma, basal canker, pine, 290. 
seedling-blight, arbor-vitae, 89. 
seedling twig-blight, juniper, 190. 
twig-blight, seedling, juniper, 190. 
Phoradendron, see Mistletoe diseases, 
general, 54. 
host index to, 57. 
Phyllactinia corylea, 153, 227, 241, 341. 
Phyllosticta, sec Leaf-spots, general, 27. 
Phyllosticta minima, 226. 

sphceropsoidea = Guignardia cesculi, 
118. 
Physalospora cydonice = Sphaeropsis ma- 

lorum, 140, 244. 
Phytophthora omnivora, 4. 
phytoptophila, Sphcerotheca, 174. 
Phytoptus, see Witches'-broom, hack- 
berry, 174. 
Pilotoe, Poly poms = Polyporus croceus, 

150, 258. 
Pin-disease, cedar, 135. 
Pine diseases, 264. 
basal canker, 290. 
blight, twig-, 272. 
blister-rusts, leaf, 265. 
Castilleja, 285. 
Comandra, 283. 
five-needle pines, 274. 
oak, 287. 
Pinon, 290. 
sweet-fern, 281. 
brown felt-blight, 271. 
brown heartwood-rot, 292. 
brown pocket heartwood-rot, 293. 
brown root- and butt-rot, 296. 



Pine diseases — Continued 

burls aiid witches'-brooms, mistle- 
toe, 273. 
butt-rot, brown, 296. 

red-brown, 294. 
canker, basal, 290. 
Castilleja rust, 285. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 
felt-blight, brown, 271. 
five-needle pine blister-rust, 274. 
freezing-to-death, roots, general, 74. 

seedlings, general, 12. 

twigs and bark, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 23. 
heartwood-rot, brown, 292. 

brown pocket, 293. 
late frost-injury, leaves, general, 21. 
leaf blister-rusts, 265. 
leaf-cast and witches'-broom o- 

western yellow pine, 271. 
leaf-cast of conifers, general, 38. 
leaf-cast of white pine, 270. 
leaf-rust, 270. 

lightning injury, general, 60. 
mistletoe burls and witches'-brooms, 

273. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
oak rust, 287. 
pecky wood-rot, 291. 
Pinon blister-rust, 290. 
red-brown root- and butt-rot, 294. 
red-brown sapwood-rot, 292. 
red-ray wood-rot, 293. 
root-rot, brown, 296. 

red-brown, 294. 
seedling, 264. 

shoe-string, general, 78. 

yellow, 296. 
rust, blister-, of five-needle pines, 
274. 

Castilleja, 285. 

Comandra, 283. 

leaf-, 270. 



INDEX 



391 



Pine diseases — Continued 
leaf blister-, 265. 
oak, 287. 

Pinon blister-, 290. 
sweet-fern, 2S1. 
sapwood-rot, red-brown, 292. 
seedling root-rot, 264. 
shoe-string root-rot, general, 78. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
sweet-fern rust, 281. 
twig-blight, 272. 
winter-drying, leaves, general, 18. 

seedlings, general, 11. 
witches'-broom of western yellow 

pine, 271. 
witches'-brooms, mistletoe burls and, 

273. 
wood-rot, pecky, 291. 

red-ray, 293. 
wood-rots, general, 64. 
yellow root-rot, 296. 
pini, Trametcs, 163, 215, 291, 324. 

Galloivaija, 270. 
pinicola, Foi7ics, 165, 184, 215, 292, 

327. 
pinipcrda, Ascocliyta, 313. 
Pinon blister-rust, 290. 
Pin-rot, cedar, 135. 
Pinus, see Pine. 
Plane-tree, see Sycamore. 
Platanus, see Sycamore. 
Plcurotus ostreatus, 235. 

ulmarius, 154. 
polychoeia, Uncinula, 173. 
PoljiJore names, synonymy of, 364. 
Polyporus amarus, 135. 
Berkeleyi, 252. 
betulinus, 113. 
borealis, 185, 329. 
carneus, 206. 
catalpce, 127. 
croceus, 150. 258. 
dryadcus, 261. 
dryophilus, 250, 310. 



Polyporus — Continued 

Ellisianus, 293. 

frondosus, 149, 259. 

obtusus, 257. 

Pilotce, 150, 258. 

Rheadcs, 250, 310. 

Schweinitzii, 91, 170, 187, 217, 294, 
331. 

squamosus, 233. 

sulphureus, 87, 124, 149, 221, 232, 
247, 340. 
Polystictus versicolor, 125. 
Poplar diseases, 298. 

butt-rot, white, 310. 

canker, 301. 

catkin-deformation, 301. 

common white wood-rot, 305. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, 47. 

frost-cracks, general, 50. 

gall, limb-, 304. 

galls, general, 63. 

gas-injury, roots, general, 76. 
smoke- and, leaves, general, 23. 

heartwood-rot, white pocket, 310. 

late frost-injury, leaves, general, 
21. 

leaf-blister, yellow, 300. 

leaf-rusts, 298. 

leaf-spots, general, 27. 

lichen-injurj', general, 52. 

lightning injury, general, 60. 

limb-gall, 304. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildew, 300. 

powdery mildews, general, 34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

rusts, leaf-, 298. 

shoe-string root-rot, general, 78. 

silver-blight, leaves, general, 41. 

silver-leaf, general, 41. 

slime-flxix, general, 53. 



392 



INDEX 



Poplar diseases — Continued 

smoke- and gas-injury, leaves, gen- 
eral, 23. 

smothering-disease, seedlings, gen- 
eral, 15. 

sooty molds, leaves, general, 41. 

sun-scald, bark, general, 52. 

sun-scorch, leaves, general, 22 
seedlings, general, 9. 

white butt-rot, 310. 

white pocket heartwood-rot, 310. 

wood-rot, common white, 305. 

wood-rots, general, 64. 

yellow leaf-blister, 300. 
Poplar rust, leaf, fir, 159. 
populea, Dolhichiza, 301. 
Populus, see Poplar. 
Poria catalpw = Polyporiis catalpw, 

127. 
Poria Weirii, 210. 
Powdery mildews, host index to, 34. 

leaves, general, 34. 
Powdery mildew, alder, 86. 

basswood, 101. 

buckeye, 121. 

elm, 153. 

hackberry, 173. 

linden, 101. 

maple, 227. 

oak, 241. 

poplar, 300. 

willow, 341. 
Powdery sapwood-rot, birch, 113. 
Pruning, tree surgery, .346. 
Pruning wounds, treatment of, 347. 
pseudo-balsaniewm, Peridermium, 156. 
Pseudotsuga, see Fir. 
Pteridis, Uredinopsis, 157. 
Puccinia fraxinata, 93. 
Pucciniastrum minimum, 180. 

myrtilli, 180. 

pustUlatum, 157. 
Puck of cypress, bald cypress, 97. 
punctatum, Rhytisma, 225. 
purpureum, Stereum, 41. 
pusilla, Razoumofskya, 321. 
pustulatum, Pucciniastrum., 157. 
pyriforme, Peridermium = Cronartium 

comandroE, 283. 
pyrolce, Melampsoropsis , 320. 
Pythium debaryanum, 3. 



Quercus, see Oak. 
quinqueseptata, Herpotrichia, 317. 

R 

radicata, Sparassis, 170, 218, 296, 331. 
radicicola. Bacillus, 88, 222. 
Razoumofskya, host index to, 55. 

see Mistletoe diseases, general, 54. 
Razoumofskya americana, 273. 

cam pylopoda, 273. 

Douglasii, 163. 

laricis, 214. 

pusilla, 321. 
Red-brown root- and butt-rot, arbor- 
vitse, 91. 

fir, 170. 

hemlock, 187. 

larch, 217. 

pine, 294. 

spruce, 331. 
Red-brown sapwood-rot, fir, 165. 

hemlock, 184. 

larch, 215. 

pine, 292. 

spruce, 327. 
Red-heart, pine, 293. 
Red leaf-blister, birch, 112. 
Red-ray wood-root, pine, 293. 
Red-rot, fir, 163. 

see Pecky wood-rot. 

see Red-ray wood-rot. 
Reinforced dressings, 351. 
Reinforcing for cavity filling, 355. 
Rheades, Polyporus, 250, 310. 
Rhizina undulata, 177, 212, 264. 
Rhizoctonia, see Damping-off, 2. 
Rhytisma aceriniim, 223. 

punctatum, 225. 

salicinum, 343. 
ribicola, Coleosporium, 269. 

Cronartium, 274. 
rimostis. Fames, 219. 
Ring-shake, fir, 163. 

see Pecky wood-rot. 
Robinia, see Locust. 
Root diseases and injuries, 72. 

drowning, general, 73. 

drying, general, 73. 

freezing-to-death, general, 74. 



INDEX 



393 



Root diseases and injuries — Continued 
gas-injury, general, 76. 
mycorhizas, general, 82. 
roots parasitized by flowering plants, 

general, 84. 
shoe-string root-rot, general, 78. 
Root-rot, brown, fir, 169. 
pine, 296. 
spruce, 329. 
red-brown, arbor-\'it2e, 91. 
fir, 170. 
.hemlock, 187. 
larch, 217. 
pine, 294. 
spruce, 331. 
seedling, hemlock, 177. 
larch, 212. 
pine, 264. 
see Damping-off, 2. 
shoe-string, general, 78. 
southern, basswood, 103. 

linden, 103. 
white, oak, 261. 
yellow, fir, 170. 
larch, 218. 
pine, 296. 
spruce, 331. 
Root-tubercles, alder, 88, 222. 
Rosellinia sp?, see Brown-mold leaf- 

bhght, 180. 
roseus, Fames, 91, 168, 184, 204, 217, 

293, 328. 
Rust diseases. 

blister-rusts, blueberry, leaf, fir, 157. 
Castilleja, pine, 285. 
Comandra, pine, 283. 
cone-, leaf- and, hemlock, 180. 
fern, leaf, fir, 156. 
fireweed, leaf, fir, 157. 
five-needle pines, 274. 
leaf- and cone-, hemlock, 180. 
leaf, fir, 155. 
pine, 265. 
spruce, 315. 
oak, pine, 287. 
Pinon, 290. 
sweet-fern, pine, 281. 
unconnected, leaf, fir, 158. 
branch-swellings, cedar, 134. 

juniper, 202. 
cedar-apples, juniper, 197. 



Rust diseases — Continued 

cone- and twig-, leaf-, hemlock, 182. 

cone-, spruce, 320. 

eastern leaf-, cedar, 129. 

eastern witches'-broom, cedar, 131. 

galls, juniper, 200. 

leaf- and stem-, juniper (general), 

192. 
leaf- and twig-, ash, 93. 

juniper, 196. 
leaf-, birch. 111. 

cone- and twig-, hemlock, 182. 

eastern, cedar, 129. 

fir, 159. 

larch, 212. 

poplar, 298. 

spruce, 316. 

western cedar, 130. 

willow, 341. 
poplar, leaf, fir, 159. 
stem-, leaf- and, juniper (general), 

192. 
twig-blight and witches'-broom, 

western, cedar, 133. 
twig-, leaf- and, ash, 93. 

juniper, 196. 
twig-, leaf-, cone- and, hemlock, 

182. 
western leaf-, cedar, 130. 
western twig-blight and witches'- 
broom, cedar, 133. 
willow, leaf, fir, 159. 
witches'-broom, eastern, cedar, 131. 

fir, 160. 

juniper, 200. 

spruce, 320. 

western twig-blight and, cedar, 
133. 



salicinum, Rhytisma, 343. 
salicis, Uncinula, 300, 341. 
Sapwood-rot, general, 64. 
powdery, birch, 113. 
red-brown, fir, 165. 
hemlock, 184. 
larch, 215. 
pine, 292. 
spruce, 327. 
uniform white, beech, 108. 
maple, 234. 



394 



INDEX 



Sapwood-rot — Continued 
white, basswood, 103. 
buckeye, 122. 
linden, 103. 
white streaked, maple, 235. 
yellowish, beech, 105. 
birch, 115. 
Schweinitzii, Polyporus, 91, 170, 1N7, 

217, 294, 331. 
Sclerotinia Fuckeliana = Botrytis cine- 

rea, 161. 
Seedling-blight, arbor-vitse, 89. 
Seedling diseases and injuries, 1. 
damping-off, general, 2. 
freezing-to-death, general, 12. 
root-rot, see Damping-off, 2. 
smothering-disease, general, 15. 
sun-scorch, general, 9. 
winter-drying, general, 11. 
Seedling, root-rot, hemlock, 177. 
larch, 212. 
pine, 204. 
twig-blight, juniper, 190. 
spruce, 313. 
septentrionale, Hydnum, 108, 234. 
Septoria, see Leaf-spots, general, 27. 
Sheet metal for cavities, 354. 
Shoe-string root-rot, general, 78. 
Silver-blight, leaves, general, 41. 
Silver-leaf, general, 41. 
Slaters' cement as a wound dressing, 

350. 
Slime-flux, general, 53. 
Smoke- and gas-injury, leaves, gen- 
eral, 23. 
Smothering-disease, seedlings, general, 

15. 
Soft heartwood-rot, oak, 257. 
solidaginis, Coleosporium, 267. 
sonchi-arvensis , Coleosporium, 266. 
Sooty molds, general, 41. 
Southern root-rot, basswood, 103. 

linden, 103. 
Sparassis radicata, 170, 218, 296, 331. 
SphcBropsis malorum, 140, 244. 
Sphceropsoidea, Phyllosticta = Guignar- 

dia cesculi, 118. 
Spharotheca lanestris, 243. 

phytoptophila, 174. 
Spraying and dusting for leaf diseases, 
357. 



Spruce diseases, 313. 
bhster-rusts, leaf, 315. 
brown felt-blight, 317. 
brown pocket heartwood-rot, 328. 
brown root- and butt-rot, 329. 
butt-rot, brown, 329. 

red-brown, 331. 
cone-rust, 320. 
cuboidal wood-rot, 329. 
damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 
felt-blight, brown, 317. 
freezing-to-death, roots, general, 
74. 

seedlings, general, 12. 

twigs and bark, 47. 
frost-cracks, 50. 
galls, general, 63. 
gas-injury, roots, general, 76. 

smoke- and, leaves, general, 23. 
heartwood-rot, brown pocket, 328. 

stringy red-brown, 328. 
leaf- and twig-blight, 319. 
leaf blister-rusts, 315. 
leaf-cast of conifers, general, 38. 
leaf-rust, 316. 

lightning injury, general, 60. 
mistletoe diseases, general, 54. 

witches'-broom, 321. 
mycorhizas, roots, general, 82. 
pecky wood-rot, 324. 
red-brown root- and butt-rot, 331. 
red-brown sapwood-rot, 327. 
root-rot, brown, 329. 

red-brown, 331. 

shoe-string,, general, 78. 

yellow, 331. 
rust, leaf blister-, 315. 

leaf-,' 316. 

witches'-broom, 320. 
sapwood-rot, red-brown, 327. 
seedling twig-blight, 313. 
shoe-string root-rot, general, 78. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 



INDEX 



395 



Spruce diseases — Continued 

stringy red-brown heartwood-rot, 

328. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
twig-blight, leaf- and, 319. 

seedling, 313. 
winter-drying, leaves, general, 18. 

seedlings, general, 11. 
witches'-broom, mistletoe, 321. 

rust, 320. 
wood-rot, cuboidal, 329. 

pecky, 324. 
wood-rots, general, 64. 
yellow root-rot, 331. 
squamosus, Polyporus, 233. 
Stem-rusts, leaf- and, juniper (general), 

192. 
Stereum purpureurn, 41. 

subpileatum, 255. 
Straw-colored butt-rot, oak, 259. 

heartwood-rot, chestnvit, 149. 
String and ray butt-rot, oak, 252. 
Stringy brown wood-rot, juniper, 209. 
red-brown heartwood-rot, fir, 16G 
hemlock, 184. 
spruce, 328. 
sirobi, Peridermium = Cronartium ribi- 

cola, 274. 
strobicola, Hypoderma, 270. 
Strumella canker, chestnut, 148. 

oak, 245. 
Strumella coryneoidea, 148, 245. 
struthiopteridis , Uredinopsis, 156. 
suaveolens, Trametes, 344. 
subpileatum, Stereum, 255. 
Sulfur dust, 358. 
sulphureus, Polyporus, 87, 124, 149, 221, 

232, 247, 340. 
Sun-scald, bark, general, 52. 
Sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
Surgery, see Tree-surgery, 345. 
Sweet-fern rust, pine, 281. 
Sycamore diseases, 333. 

damping-off, seedlings, general, 2. 
drought-injury, leaves, general, 22. 
drowning, roots, general, 73. 
drying, roots, general, 73. 
electrical injuries, general, 60. 



Sycamore diseases — Continued 

freezing-to-death, roots, general, 74. 

seedlings, general, 12. 

twigs and bark, 47. 
frost-cracks, general, 50. 
galls, general, 63. 
gas-injurj', roots, general, 76. 

smoke- and, leaves, general, 23. 
late frost-injiu"y, leaves, general, 

21. 
leaf- and twig-blight, 333. 
leaf -spots, general, 27. 
lichen-injury, general, 52. 
lightning injury, general, 60. 
mistletoe diseases, general, 54. 
mycorhizas, roots, general, 82. 
powdery mildews, general, 34. 
root-rot, shoe-string, general, 78. 
roots parasitized by flowering plants, 

general, 84. 
shoe-string root-rot, general, 78. 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 

sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
twig-blight, leaf- and, 333. 
wood-rots, general, 64. 



Taphrina aurea, 300. 

carnea, 112. 

caeridescens, 239. 

Johansonii, 301. 
Tar, as a wound dressing, 348. 
Tar leaf-spot, maple, 223. 

willow, 343. 
Taxodium, see Bald cypress. 
Temperature injuries, 

drought-injury, leaves, 22. 

freezing-to-death, roots, 74. 
seedlings, 12. 
twigs and bark, 47. 

frost-cracks, 50. 



396 



INDEX 



Temperature injuries — Continued 

late frost-injury, leaves, 21. 

sun-scald, bark, 52. 

sun-scorch, leaves, 22. 
seedlings, 9. 

winter-drying, leaves, 18. 
seedlings, 11. 
terebinthinacece, Coleosporium, 269. 
texanus, Fomes, 209. 
Thelephora laciniata, 15. 
Thielavia basicola, 4. 
Thuja, see Arbor- vitse. 
thujina, Keithia, 90. 
TUia, see Basswood. 
tilice, Cercospora, 102. 
tinctorium, Echinodontium, 166, 184, 

328. 
Tinning cavities, 354. 
Tools for tree surgery, 346, 352, 353. 
Top-rot, see red-ra.y wood-rot. 
trachysorum, Gytnnosporanghim, 201. 
Trametes, pini, 163, 215, 291, 324. 

suaveolens, 344. 
Tree names, common, 361. 

scientific, 361. 
Tree surgery, 345. 

cavity treatments, 353. 

disinfecting wounds, 348. 

dressings, wound, 348. 

lesion excision, 351. 

pruning, 346. 

publications on, 369. 

wound dressings, 348. 

wounds, disinfecting, 348. 
tri?ia, Erysiphe, 241. 
Tsuga, see Hemlock. 
tsugw, Keithia, 179. 
tumefaciens, Bacterium, 304. 
Twig-blight, chestnut, 140. 

oak, 244. 

pine, 272. 

plane-tree, 333. 

spruce, 319. 

sycamore, 333. 
Twig-blight, gray mold, fir, 161. 

seedling, juniper, 190. 
spruce, 313. 

western, cedar, 133. 
Twig-rust, leaf- and, ash, 93. 

leaf- and, juniper, 196. 

leaf-, cone- and, hemlock, 182. 



U 



ulmarius, Pleurotus, 154. 
ulmea, Gnomonia, 152. 
Ulmus, see Elm. 
Uncinula circinata, 227. 

Clintonii, 101. 

flexuosa, 121. 

macrospora, 153. 

parvida, 173. 

polychceta, 173. 

salicis, 300, 341. 
Unconnected rusts, leaf, fir, 158. 
undulata, Rhizina, 177, 212. 
Uniform white sapwood-rot, beech, 
108. 

maple, 234. 
Uredinopsis Atkinsonii, 156. 

mirabilis, 156. 

osmundce, 156. 

phegopteridis, 156. 

pteridis, 157. 

struthiopteridis, 156. 



velutipes, CoUybia, 103, 122. 
veneta, Gnomonia, 237, 333. 
vernonice, Coleosporium, 267. 
versicolor, Polystictus, 125. 
Verticillium, wilt, maple, 231. 
virginiana, Epiphegus, 108. 
Volutella, 4. 

W 

Walnut diseases, 339. 

brown checked wood-rot, 340. 

common white wood-rot, 339. 

leaf-spot, 339. 

see all diseases listed under Butter- 
nut diseases. 

wood-rot, brown checked, 340. 
common white, 339. 
Weirii, Chrysomyxa, 316. 

Poria, 210. 
Western leaf-rust, cedar, 130. 

twig-blight and witches'-broom, ce- 
dar, 133. 
Wet heartwood-rot, oak, 254. 
White bark, juniper, 204. 



INDEX 



397 



White butt-rot, beech, 108. 

birch, 117. 

maple, 236. 

oak, 260. 

poplar, 310. 
White heartwood-rot, ash, 95. 
White piped butt-rot, chestnut, 150. 

oak, 258. 
White pocket heartwood-rot, juniper, 
206. 

oak, 250. 

poplar, 310. 
White root-rot, oak, 261. 
White sapwood-rot, basswood, 103. 

buckeye, 122. 

linden, 103. 
White strand wood-rot, maple, 233. 
White streaked sapwood-rot, maple, 

2.35. 
White wood-rot, oak, 260. 

willow, 344. 

see common white wood-rot. 
Willow diseases, 341. 

common white wood-rot, 343. 

damping-off, seedlings, general, 2. 

drought-injury, leaves, general, 22. 

drowning, roots, general, 73. 

drying, roots, general, 73. 

electrical injuries, general, 60. 

freezing-to-death, roots, general, 74. 
seedlings, general, 12. 
twigs and bark, 47. 

frost-cracks, general, 50. 

galls, general, 63. 

gas-injury, roots, general, 76. 
smoke- and, leaves, general, 23. 

late frost-injury, leaves, general, 21. 

leaf-rusts, 341. 

leaf-spot, tar, 343. 

leaf-spots, general, 27. 

lichen-injury, general, 52. 

lightning injury, general, 60. 

mistletoe diseases, general, 54. 

mycorhizas, roots, general, 82. 

powdery mildews, 341. 
general, .34. 

root-rot, shoe-string, general, 78. 

roots parasitized by flowering plants, 
general, 84. 

rusts, leaf-, .341. 

shoe-string root-rot, general, 78. 



Willow diseases — Continued 
silver-blight, leaves, general, 41. 
silver-leaf, general, 41. 
slime-flux, general, 53. 
smoke- and gas-injury, leaves, gen- 
eral, 23. 
smothering-disease, seedlings, gen- 
eral, 15. 
sooty molds, leaves, general, 41. 
sun-scald, bark, general, 52. 
sun-scorch, leaves, general, 22. 

seedlings, general, 9. 
tar leaf-spot, 343. 
white wood-rot, 344. 
wood-rot, common white, 343. 

white, 344. 
wood-rots, general, 64. 
Willow rust, leaf, fir, 159. 
Wilt, m.aple, 231. 
Winter-drying, leaves, general, 18. 

seedlings, general, 11. 
Winter-injuries, see Temperature inju- 
ries. 
Witches'-broom, curled leaf-blight and, 
buckeye, 121. 
eastern, cedar, 131. 
hackberry, 174. 
mistletoe burl and, fir, 163. 
larch, 214. 
pine, 273. 
mistletoe, spruce, 321. 
rust, juniper, 200. 

spruce, 320. 
western, cedar, 133. 
western yellow pine, 271. 
Witches'-broom, see Leaf-cast of coni- 
fers, general, 38. 
see Mistletoe diseases, general, 54. 
Wood-rot, brown, elm, 154. 
brown checked, alder, 87. 
butternut, 124. 
chestnut, 149. 
locust, 221. 
maple, 232. 
oak, 247. 
walnut, 340. 
common white, alder, 87. 
beech, 107. 
birch, 115. 
butternut, 124. 
hickory, 189. 



398 



INDEX 



Wood-rot — Continued 

maple, 232. 

oak, 250. 

poplar, 305. 

walnut, 339. 

willow, 343. 
cuboidal, hemlock, 185. 

spruce, 329. 
pecky, fir, 163. 

larch, 215. 

pine, 291. 

spruce, 324. 
red-ray, pine, 293. 
ring-shake, see Pecky. 
stringy brown, juniper, 209. 
white, oak, 260. 

willow, 344. 
white strand, maple, 233. 
yellow, juniper, 208. 

locust. 219. 
yellowish, catalpa, 125. 
Wood-rots, cavity treatments, surgery, 
353. 
control of, 70, 351, 353. 
disinfecting wounds, surgery, 348. 
dissemination of the spores, 69. 



Wood-rots — Continued 

general, 64. 

infection, modes of, 65. 

lesion excision, surgery, 351. 

see Heartwood-rot. 

see Sapwood-rot. 

tree surgery, 345. 

wood-decay, nature of the process, 
67. 

wound dressings, surgery, 348. 
Wound, disinfecting, surgery, 348. 

dressings, surgery, 348. 



Yellow leaf-blister, birch, 112. 

poplar, 300. 
Yellow root-rot, fir, 170. 

larch, 218. 

pine, 296. 

spruce, 331. 
Yellow wood-rot, jimiper, 208. 

locust, 219. 
Yellowish sapwood-rot, beech, 105. 

birch, 115. 
Yellowish wood-rot, catalpa, 125. 



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